I use foursquare and it can be quite helpful when in a new town for a night of partying. However, it is missing something. Badges are sorta cool but it is super easy for people to cheat. It's very open ended which is also good but it should give me more incentive to use it.
I may hate facebook but I do have it on my phone. Maybe foursquared patented certain things? I really don't know.
Oh, and does anyone know a stalker by the name of Topguest?