Neal Pollack wrote a great piece for Wired Magazine which looks behind the scenes of the start and growth of both Gowalla and Foursquare. I use Gowalla and picked it mostly because I love the look and feel of it over Foursqaure. But I always assumed the two apps were basically the same. And though it’s true that they both have the same foundational usage — go places and get rewards for checking in — the two apps reward and encourage those check-ins quite differently.