Here’s a refreshingly skeptical look at social networking sites. How relevant are they? How long will people use them? Are they going to make their owners billions from advertising? And, of course, the giant unsaid question: what’s after MySpace and Facebook? Aren’t people getting tired of creating a personal profile at this point?

Facebook’s inclusiveness has broadened its popular appeal, but the alchemy of the Web is converting eyeballs to dollars via the “click-throughs” that advertisers crave–and the social nets are still searching for the magic formula. Members of both Facebook and its chief rival, MySpace, spend on average about 3 1/2 hours a month clicking around on each site, but they get so caught up in checking out their friends’ pages and updating their own that they are less likely to click through to the ads. What’s more, Facebook may not be able to keep up the momentum of its rapid-fire growth because social-networking aficionados are notoriously fickle. Remember Friendster?

Social networks are a lot like nightclubs, and Friendster was the place to be in 2004 and ‘05, before MySpace came along and stole its mojo. In short, Friendster got boring. “It’s like a high school dance,” says Max Levchin, CEO of Slide, a top maker of image-based applications for social networks. “Everyone shows up and nobody does anything, because there’s nothing to do.”

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