I agree--I was thinking of solutions to this, and the most immediate thing that comes to mind is that you have to be extremely proactive in capturing small grou

I agree--I was thinking of solutions to this, and the most immediate thing that comes to mind is that you have to be extremely proactive in capturing small groups of people who are already organized around each other. If you have a start-up community in a college area, for instance, go out of your way to facilitate student organizations (and don't just send out a few emails to potential users). If your community has the ability to organize events, and and the salsa dancing club secretary doesn't want to have to deal with setting stuff up, sponsor their club with money or do it yourself.