Six Degrees Co.

To attract users, Currier's matchmaking company, Tickle Inc., recently incorporated a software feature called social networking into its website. The six-degrees-of-separation software links people through their mutual business or personal connections, allowing them to mine their friends (and their friends' friends) for sales leads, job-hunting tips, friendship, or dates.

The digerati are anointing social networks, of which Friendster is the early leader with more than 4 million registered members, with lofty monikers like "Internet 2.0" and "the people web." If the Internet's first stage, they say, was about publishing what people know, this next stage is about exploiting who people know.

Take Liz Garcia, a TV and film writer in Los Angeles. After receiving an invitation by e-mail from a friend last spring, Garcia created a Friendster profile listing her age (26), relationship status (in one), hometown (Ridgefield, Conn.), interests ("the outdoor sports I will someday participate in"), and favorite movies ("Rosemary's Baby" and "Sixteen Candles"), then built her network to its current size of 90 direct friends.

By browsing through the thousands of profiles linked to by her friends, and by using Friendster's search engine, Garcia discovered that she is two degrees removed from comedian Margaret Cho and three degrees away from actor Thomas Lennon. She found old friends from summer camp, set up friends on dates, and helped plan a high school reunion through Friendster. "I'm a little bit addicted," she said.

So are some of the West Coast's top-tier venture capitalists. They have jumped into social networking wholeheartedly, leading a spree of investments, mergers, and patent fights. Investors diving in during the past two months include Kleiner Perkins Caufield & Byers, Benchmark Capital, Sequoia Capital, and the California office of Wellesley's Battery Ventures. The prestigious VC firm Mayfield and media heavyweights Knight Ridder Inc. and Washington Post Co. recently invested $6.3 million in Tribe Networks, praising its Friendster-like Tribe.net website as "an early leader in trusted person-to-person online classifieds."

But in dubbing social networking Internet 2.0, some venture capitalists and academics warn, investors may be forgetting some of the lessons of Internet 1.0.

"We've created this little bubble again with high prices and high expectations," said Andrew Anker, a venture partner with August Capital, which invested in Tickle, then known as Emode Inc., in 2000. "Social networking may get killed, not because it's not interesting, but because we ratchet up expectations too quickly."

Skeptics believe that few people will pay for these social networking services alone. Anker predicts that social networking will become a must-have free feature for dating services and other Internet businesses, much like Web-based e-mail became for Internet portals in the mid-1990s.

Tickle, for example, makes its money by selling personality tests and by connecting compatible singles through their similar interests and test results. Currier said the closely held company was profitable each of the last six quarters, although he would not say how profitable. After seeing the early success of Friendster, however, Tickle in September added a free social networking section on its website that lets users meet through their mutual friends. Within two months 650,000 people created profiles. Tickle then acquired Ringo, a social networking site with 350,000 users, for an undisclosed amount.

Currier and Anker want to exploit the "viral marketing" of social networks -- that is, they hope users invite friends to join, and those friends pay for Tickle's subscription services.

Other Internet businesses are trying a similar approach. Evite, an online party invitation service owned by Barry Diller's InterActiveCorp, added free social networking features last month. Evite, which relies on advertising revenue, hopes people will browse the user profiles to learn about partygoers before an event, or even to meet up with companions for activities that they may plan on Evite.

"No one has cracked the code on that yet, of how you make someone pay for these social networking sites," said Evite president John Foley.

Monster.com, a job-search website based in Maynard, plans to launch a social networking service for career development called Monster Networking early next year. Users will be able to search through the profiles of other members without charge, but Monster expects to ask them to pay subscription fees for the ability to contact other members.

The fact that questions remain about the business model for social networking companies didn't stop Kleiner Perkins, Benchmark, and Battery from investing $13 million in Friendster Inc., based in Sunnyvale, Calif. Friendster said in an October news release that it plans to keep its basic services free but eventually sell subscriptions for some premium services.

Today's social networking applications employ theories that have been kicked around in academia and popular culture since Harvard University psychologist Stanley Milgram found in 1967 that most people on earth are separated by fewer than six degrees. The Kevin Bacon Game, in which players try to link actors to Bacon through their costars, is one example. The best way to meet people for dating, friendship, or business, the theory of these services goes, is to find them through your friends, the friends of your friends, and the friends of your friends' friends. The early social-networking website Sixdegrees.com was launched in 1996 and garnered more than 3 million members but shut down in 2000 after it failed to turn a profit.

"The timing was a bit too early," said Stan Fung, a managing director with Zero Stage Capital in Cambridge. He considered investing in social-networking companies but ultimately decided that only the very few start-ups that best execute their business plans will survive -- a better fit for West Coast venture capitalists willing to take more risks.

Where Sixdegrees.com failed, Friendster is translating a geeky idea to the computer-using masses much like Netscape did for Internet browsers, said Elizabeth Lane Lawley, an assistant professor at the Rochester Institute of Technology.

"The question is whether there is a stand-alone business model," she said.

Services like Spoke, Ryze, Visible Path, LinkedIn, and Boston-based Contact Network think the real money is in helping executives mine the connections of their friends and colleagues for help finding sales leads, potential employees, and investors. Francois Gossieaux trawled LinkedIn while founding a software start-up in Andover. He plans to hire a product manager he found through the service, if a venture capitalist who found him through LinkedIn gives seed money.

David Flaschen, a managing director in the Cambridge office of Flagship Ventures, a bicoastal venture capital firm, said he has been closely watching 15 business-oriented social networking sites with thoughts of investing. West Coast venture capitalists have been much quicker than Boston-area firms to fund consumer-focused sites like Friendster, he said, because the California firms are all afraid of missing out on the successor to the last great consumer Web phenomenon: Google Inc., the search engine company that turned its rapid user growth into hefty profits. They don't worry about profits "when they see subscription rates go from zero to a few million in a few months," he said.

Mark Kvamme, a partner with Sequoia, a firm in Menlo Park, Calif., that invested $4.7 million in LinkedIn, said venture capitalists have largely invested responsibly in social networking companies.

But Tickle said it's not counting on the technology alone to keep its business going.

"Let's not confuse the excitement around an emerging space with an established business model," said Samir Arora, the company's chairman. "If we were just a social networking company, the stakes would be very different."

Chris Gaither can be reached at gaither@globe.com.