Why do you use Foursquare (or Gowalla)?
What is the appeal of Foursquare/Gowalla? Is the value in the competition, or exploring new places? What makes you pull it out of your pocket to check-in?
I do think the concept of checkins and such is something VERY powerful for businesses. I think there's more use in "geo-physical social bookmarking" ie- I can favorite and show people what I like, while getting deals from businesses. The whole mobile social networking thing is just a feature to me and I'm waiting for facebook to do it. What delicious did for internet bookmarks, is what I see foursquare or some service like it doing in the future for physical objects.