It's a tough problem – no doubt about it. In v1, as we expect your nearby network to be quite small, we've focused heavily on your existing friends network (from facebook) and are trying to make that experience as good as possible. Inviting them, organising the events, etc.

In the past, just like you, we used facebook groups and/or messages/chats back and fourth to friends.

Hopefully the app will be good enough for people to start out with their existing friends and then more and more people nearby will show up.