If Slide is at all familiar, it's as a knockoff of Flickr, the photo-sharing site. Users upload photos, which are displayed on a running ticker or Slide Show, and subscribe to one another's feeds. But photos are just a way to get Slide users communicating, establishing relationships, Levchin explains.

The site is beginning to introduce new content into Slide Shows. It culls news feeds from around the Web and gathers real-time information from, say, eBay auctions or Match.com profiles. It drops all of this information onto user desktops and then watches to see how they react.

Suppose, for example, there's a user named YankeeDave who sees a Treo 750 scroll by in his Slide Show. He gives it a thumbs-up and forwards it to his buddy" we'll call him Smooth-P. Slide learns from this that both YankeeDave and Smooth-P have an interest in a smartphone and begins delivering competing prices. If YankeeDave buys the item, Slide displays headlines on Treo tips or photos of a leather case. If Smooth-P gives a thumbs-down, Slide gains another valuable piece of data. (Maybe Smooth-P is a BlackBerry guy.) Slide has also established a relationship between YankeeDave and Smooth-P and can begin comparing their ratings, traffic patterns, clicks and networks.

Based on all that information, Slide gains an understanding of people who share a taste for Treos, TAG Heuer watches and BMWs. Next, those users might see a Dyson vacuum, a pair of Forzieri wingtips or a single woman with a six-figure income living within a ten-mile radius. In fact, that's where Levchin thinks the first real opportunity lies - hooking up users with like-minded people. "I started out with this idea of finding shoes for my girlfriend and hotties on HotorNot for me," Levchin says with a wry smile. "It's easy to shift from recommending shoes to humans."

If this all sounds vaguely creepy, Levchin is careful to say he's rolling out features slowly and will only go as far as his users will allow. But he sees what many others claim to see: Most consumers seem perfectly willing to trade preference data for insight. "What's fueling this is the desire for self-expression," he says.