I’ve played with a batch of location based social apps on my G1 (gowalla, foursquare, where, latitude among others). I like the idea of knowing if friends/colleagues are in the neighborhood or seeing reviews of restaurants, galleries, parks, etc. from people I know, but the numbers of other users is dismally small.
Support isn’t in the android Facebook app and I don’t expect it for a few months as it’s kind of the red-headed stepchild platform from Facebook’s point of view. It also hasn’t yet appeared on touch.facebook.com for me. Assumably, they are rolling it out across servers a bit slowly to make sure that it scales. There are some privacy oddities (friends can check me into locations without me knowing?) but they’ll work those out.
The thing that particularly strikes me about location based social though, is that it doesn’t require a smart phone. A bar or park can put a check-in shortcode on their menu/coasters. Sending an SMS can check me in, allow the place to give send me a 5% discount SMS for checking in as a first time customer, send back an SMS with the names of friends who are nearby, etc. Dodgeball did all that stuff 5-6 years ago. Google shut it down after buying it, but it seems a safe bet that those services will be under the hood of Google’s location-based product offering that is coming down the pipe.