It's like Facebook for the people you spend time with without adding as friends; Foursquare for people that aren't motivated to deliberately broadcast their whereabouts; Grindr for people in your area not looking to hook up.

The underlying technology sounds like it could be useful for everyone from Facebook to the FBI, but the service itself has more buzzwords than users in my area, and I don't see too many reasons why that state of affairs should change dramatically...