> Foursquare already had a massive database of check-ins — location information about the places its users most liked to go. And this data didn’t just include the place where someone had checked in. It showed how strong the GPS signal was at the time, how strong each surrounding Wi-Fi hotspot signal was, what local cell towers were nearby, and so on. Leveraging this data meant that Foursquare could still grab a good current location even if users were underground, near a source of radio interference, or facing some other signal obstacle. Chances are, some prior Foursquare user had seen the world through the same flawed eyes and reported his or her location.

This sounds more valuable as a technology than the social network side of the business itself.

If another company wanted to build up a similar database of location information, they could send out a fleet of its own staff all over the world to collect it, à la Google's Street View cars. But Foursquare has managed to sidestep all of this expense and infrastructure by harnessing its userbase as a massive, free source of data input.

Through badges, recommendations, and deals with local stores, they've created an incentive to provide the data they need. And through the mechanisms they have to prevent cheating in the game side of things, they've accidentally developed a way to ensure the accuracy of the location information their system can provide.

Licensing out this technology could become the long-sought-after profit engine for Foursquare, paying the bills for the flashy social network layer on top that keeps the data flowing in.