Is Foursquare for Booksellers?

You may have already heard of the two year-old social networking/social gaming site Foursquare. Basically, Foursquare is a mobile-phone-based (iPhone and Android) online service where friends earn points by tagging actual places they go, kind of like an elaborate, real-life scavenger hunt. The network is meant to help businesses draw customers while also creating a social network that fits into a non-computer-based social life.