Foursquare vs. Gowalla: Inside the Check-In Wars

If you ever visit the downtown Manhattan offices of Foursquare, the popular location-based social game for smartphones, don't say the word Gowalla. When I made that mistake during a visit there last November, 27-year-old cofounder Naveen Selvadurai sent me to the Foursquare time out chair. It was a joke. I think.

Gowalla is Foursquare's arch-rival. The companies both launched eight months earlier at the South by South West interactive festival. Their products pioneered the then-uncharted...