Facebook helps social start-ups gain users

: Jenna Wortham

The only thing more challenging than deciphering the names of all the social-minded websites battling for attention at the South by Southwest Technology Conference in Austin, Texas—Brizzly, Vicarious.ly, Stalqer, Quora and so forth—would be the chore of signing up for each one individually.

But a growing number of start-up companies are getting around this problem by, in essence, outsourcing the sign-up process. They are making use of a Facebook service that lets users log into new sites using their Facebook credentials. The free service, Facebook Connect, can help nascent Web services recruit a healthy crowd of users in a hurry, and help the users find their friends on those sites.

At the same time, the service reinforces Facebook’s role as the central hub of the social networking world. “There is always a chicken-and-egg problem with any social service,” said Mark Hendrickson, co-founder of a service called Plancast, which lets members share their social or business plans with their online circle of friends. “You have to have friends there already to make it valuable.”

Relying on another company for such an important function can be risky. For example, an unexpected technical problem at Facebook could affect a start-up’s site. More broadly, any big change in the way Facebook works could have ripple effects. Hendrickson acknowledged those challenges, saying, “These platforms are essential for next-generation technologies, but they are also still minefields for those same new technologies.”

Most sites hedge their bets by also creating ways for people to sign up directly, or to use their log-in information from Twitter, in addition to Facebook, as Plancast has elected to do.

Of course, coming up with a clever idea and synching it to Facebook Connect does not guarantee a home run. Gelato, a matchmaking service that finds other lovelorn people in your social circle, failed to gain much traction after it was introduced last fall.

On the other hand, Aardvark, which lets users seek answers to questions from people in their extended online network, was bought by Google for a reported $50 million last month.

Facebook Connect has helped give rise to a new wave of social Web services that benefit from piggybacking on Facebook and its 400 million users. Blippy, for example, is a new service that allows members to give friends a glimpse into their spending habits by showing purchases made through iTunes and Netflix and on major credit cards.

“There hasn’t been a big forum for talking...