Most of the time when I would use such an app the people locally around me are not connected to me in any way - like in a bar or a cafe.

Will a social recluse build the next social network? It seems a bit counter intuitive, but then it's supposed to have worked for Mark Zuckerberg. Certainly a lot of people would appreciate networking without investing any work. No more "become my friend" button - just stand next to somebody and kaboom, you have a new friend.