For a Web site, it could hardly look less exciting. Its pages are heavy with text, much of it a flat blue, and there are few photos and absolutely no videos.

But LinkedIn, the social network for professionals, is dull by design. Unlike Facebook and MySpace, the site is aimed at career-minded, white-collar workers, people who join more for the networking than the social.

Now, in the midst of Silicon Valley’s recession-proof enthusiasm for community-oriented Web sites, the most boring of the social networks is finally grabbing the spotlight.

On Wednesday, LinkedIn will announce that it has raised $53 million in capital, primarily from Bain Capital Ventures, a Boston-based private equity firm. The new financing round values the company at $1 billion. That heady valuation is more than the $580 million that the News Corporation paid for MySpace in 2005, but less than the $15 billion value assigned to Facebook last year when Microsoft bought a minority stake.

LinkedIn’s investment round delays a rumored initial public offering, which would have finally tested the public market’s interest in social networking.

“What we didn’t want is to have the distraction of being public and to be worried by quarterly performance,” said Dan Nye, the buttoned-down chief executive of LinkedIn, who would not be caught dead in the Birkenstocks and rumpled T-shirts favored by MySpace and Facebook employees.

LinkedIn, which says it is already profitable, will use the investment to make acquisitions and expand its overseas operations.

“We want to create a broad and critical business tool that is used by tens of millions of business professionals every day to make them better at what they do,” Mr. Nye said.

The average age of a LinkedIn user is 41, the point in life where people are less likely to build their digital identities around dates, parties and photos of revelry.

LinkedIn gives professionals, even the most hopeless wallflower, a painless way to follow the advice of every career counselor: build a network. Users maintain online résumés, establish links with colleagues and business acquaintances and then expand their networks to the contacts of their contacts. The service also helps them search for experts who can help them solve daily business problems.

The four-year-old site is decidedly antisocial: only last fall, after what executives describe as a year of intense debate, did the company ask members to add photos to their profiles.

That business-only-please strategy appears to be paying off. The number of people using LinkedIn, based in Mountain View, Calif., tripled in May over the previous year, according to Nielsen Online. At 23 million members, LinkedIn remains far smaller than Facebook and MySpace, each with 115 million members, but it is growing considerably faster.

LinkedIn also has a more diversified approach to making money than its entertainment-oriented rivals, which are struggling to bring in ad dollars and keep up with inflated expectations for increased revenue.

LinkedIn will get only a quarter of its projected $100 million in revenue this year from ads. (It places ads from companies like Microsoft and Southwest Airlines on profile pages.) Other moneymakers include premium subscriptions, which let users directly contact any user on the site instead of requiring an introduction from another member.

A third source of revenue is recruitment tools that companies can use to find people who may not even be actively looking for new jobs. Companies pay to search for candidates with specific skills, and each day, they get new prospects as people who fit their criteria join LinkedIn.

LinkedIn is set to undergo a radical shift in strategy to find other sources of revenue. Instead of catering primarily to individual white-collar workers, the site will soon introduce new services aimed at companies. It is a risky move that could alienate members who prefer to use the networking site to network — without their bosses peering over their shoulders.

One new product, Company Groups, automatically gathers all the employees from a company who use LinkedIn into a single, private Web forum. Employees can pose questions to each other, and share and discuss news articles about their industry.

Soon, LinkedIn plans to add additional features, like a group calendar, and let independent developers contribute their own programs that will allow employees to collaborate on projects.

The idea is to let firms exploit their employees’ social connections, institutional memories and special skills — knowledge that large, geographically dispersed companies often have a difficult time obtaining.

Zooped,Facebook, MySpace and other Web sites have unleashed a potent new phenomenon of social networking in cyberspace. But at the same time, a growing body of evidence is suggesting that traditional social networks play a surprisingly powerful and underrecognized role in influencing how people behave.

The latest research comes from Nicholas A. Christakis, a medical sociologist at the Harvard Medical School, and James H. Fowler, a political scientist at the University of California at San Diego. The pair reported last summer that obesity appeared to spread from one person to another through social networks, almost like a virus or a fad.

In a follow-up to that provocative research, the team has produced similar findings about another major health issue: smoking. In a study published last week in the New England Journal of Medicine, the team found that a person’s decision to kick the habit is strongly affected by whether other people in their social network quit — even people they do not know. And, surprisingly, entire networks of smokers appear to quit virtually simultaneously.

Taken together, these studies and others are fueling a growing recognition that many behaviors are swayed by social networks in ways that have not been fully understood. And it may be possible, the researchers say, to harness the power of these networks for many purposes, such as encouraging safe sex, getting more people to exercise or even fighting crime.

“What all these studies do is force us to start to kind of rethink our mental model of how we behave,” said Duncan Watts, a Columbia University sociologist. “Public policy in general treats people as if they are sort of atomized individuals and puts policies in place to try to get them to stop smoking, eat right, start exercising or make better decisions about retirement, et cetera. What we see in this research is that we are missing a lot of what is happening if we think only that way.”

For both of their studies, Christakis and Fowler took advantage of detailed records kept between 1971 and 2003 about 5,124 people who participated in the landmark Framingham Heart Study. Because many of the subjects had ties to the Boston suburb of Framingham, Mass., many of the participants were connected somehow — through spouses, neighbors, friends, co-workers — enabling the researchers to study a network that totaled 12,067 people.

When researchers analyzed the patterns of those who managed to quit smoking over the 32-year period, they found that the decision appeared to be highly influenced by whether someone close to them stopped. A person whose spouse quit was 67 percent more likely to kick the habit. If a friend gave it up, a person was 36 percent more likely to do so. If a sibling quit, the chances increased by 25 percent.

A co-worker had an influence — 34 percent — only if the smoker worked at a small firm. The effects were stronger among the more educated and among those who were casual or moderate smokers. Neighbors did not appear to influence each other, but friends did even if they lived far away.

“You appear to have to have a close relationship with the person for it to be influential,” Fowler said.

But the influence of a single person quitting nevertheless appeared to cascade through three degrees of separation, boosting the chance of quitting by nearly a third for people two degrees removed from one another.

“It could be your co-worker’s spouse’s friend or your brother’s spouse’s co-worker or a friend of a friend of a friend. The point is, your behavior depends on people you don’t even know,” Christakis said. “Your actions are partially affected by the actions of people who are beyond your social horizon” — but in the broader network.

In addition, the researchers found that the size of smokers’ own networks did not change over time, even though the overall number of smokers plummeted, from 45 percent to 21 percent of the population during that time. The researchers realized that what happened was that entire networks of smokers would quit almost simultaneously

If you’re part of my generation, online social networking is a part of life. When you meet someone at a party and you hit it off, you ask if they’re on Facebook. If you meet a band, they’ll likely give you their Myspace Web address. Your photos are probably on Flickr for your friends and family to see. Maybe you have a blog or Web journal to update the world on your life.

Now there is an online community for those who are trying to better their financial situation: Debtsy.com, a new Web site I read about on WalletPop. “Debtsy is a place where you can connect with others as you eliminate debt and build wealth,” the site’s tagline says.

On the site, you can blog about your money situation, track your net worth, learn to invest and join a network of people who have the same goals. The site also has many different groups you can join and participate in, ranging from students working to pay off education loans and credit card debt to wannabe investors trying to learn the tricks of the trade. You also have the ability to control who sees your information, which is vital in online communities.

Your location on a friend network, a photo on Facebook, a prayer for a deployed family member on a military-based blog – all posted on the World Wide Web with the intent to bring comfort to loved ones and news to friends. This information may seem harmless, but when put together these puzzle pieces show a picture with more information than military members should share.

Col. Andy Pears, director of Communications and Information for Headquarters Air University, became a “completely fictional” staff sergeant on a social networking site designed for military members to demonstrate the amount of information available. The “sergeant” said he had no trouble creating a profile and false identity.

With a few mouse clicks, Colonel Pears found combat and operations histories, pictures from inside deployed locations, descriptions and duties within that location and details about military members receiving medals. There is never an attempt to confirm military affiliation, he said.

At the beginning of the year, MySpace.com was on top of the social-networking heap. And as 2007 draws to a close, the News Corp.-owned site is still far ahead in page views and user accounts. It continues to expand into both new language markets and original media content like the Web series Quarterlife, and it has earned critical acclaim for the interactive “presidential dialogues” that it organized in conjunction with MTV. Parent company Fox Interactive Media has also expanded its social-media offerings, acquiring image-sharing site Photobucket and widget start-up Flektor.

New social-networking start-ups also flooded the Web (MC Hammer, anyone?) and big names like Yahoo and Viacom made plays in the field, as well (Mash and Flux, respectively).

But this was the year that Facebook caught fire, and even a court battle over the site’s true origins couldn’t stop its momentum for much of 2007.

The real game changer came on May 24, when 23-year-old Facebook CEO Mark Zuckerberg announced that the site was releasing code that would let third-party developers create applications to run within the service. Experts considered the Facebook Platform launch a milestone in the evolution of social networks, and developers saw it as their ticket to success. Start-ups devoted entirely to embeddable social-network widgets, like Slide and RockYou, became some of Silicon Valley’s hottest new companies.

Soon after, other social networks decided to follow suit. MySpace, LinkedIn, Bebo, and others all announced that they would be opening their services to developer applications, too. Google, meanwhile, had its own plan: the search giant unveiled OpenSocial, a standard that any social network could use for a developer platform. With just about every major social media player onboard except Facebook, OpenSocial was the only real threat to the Facebook platform that emerged in 2007.

The hype culminated when Microsoft confirmed that it would invest $240 million in Facebook, putting the social network’s estimated value at a jaw-dropping $15 billion. But things started to unwind when several activist groups, including MoveOn.org, alleged that Facebook was violating user privacy through its new Beacon advertisements, which shared information about users’ activity on retail partners’ sites with their Facebook friends. In the wake of the accusations, Facebook apologized and added more privacy controls, much as it had done a year earlier when users protested the debut of the “news feed.”

Smaller social networks also made headlines. The much-talked-about Digg remained a hot topic. Acquisition rumors floated around late in the year, and in the spring, some ugly legal action almost unfolded when the site refused to obey a Digital Millennium Copyright Act (DMCA) takedown notice. Twitter, a start-up devoted to “microblogs” where no entry is longer than 140 characters, took off at the South by Southwest Interactive Festival in March. Meanwhile, its chief rival Jaiku was snapped up by Google.

Some of the year’s other social-media acquisitions included music-based network Last.fm, purchased by CBS Interactive; kids’ site Club Penguin, acquired by Disney; StumbleUpon, which eBay bought; and Clipmarks, acquired by Forbes Media.

Not surprisingly, privacy and safety issues remained on the horizon. Both Facebook and MySpace grappled with demands from state attorneys general who were concerned that young people could be exposing themselves to online threats through social networks. Their efforts didn’t do much to stall either site, but served as a continual reminder that even though Silicon Valley might tout a company as the future of communication, legal authorities might beg to differ.
By Caroline McCarthy