I'd join a community primarily because I'm interested in the same thing, not because I want to find somewhere to sell / market research. Most communities will reject you for too much business unless it's a part of who they are or you've been around long enough to know how this is normal done and received.
I would not say I crafted a community (trying to do that now actually). More that I'm a developer and we hang out in certain places, and that I simply hung out
