I've been thinking about a real-world analogue for these types of social communities (e.g. synagogues) that actually makes money. The only one I can come up with is something like a fraternity. You pay dues, and have a local chapter that's also part of a larger national organization.

I'm not a giant fan, but it's very similar to the App.net model. Obviously you don't see massive scale, but you do get money without interfering with the social dynamic. Interestingly, the very fact that it costs money may make it more appealing to join. Curious to see where that goes.