Invite-only would get rid of people like me, who come here to learn from those who are able to do, with hopes that one of these days I'll be able to do it myself. I lurk, yes, and only try to comment when I feel I can contribute to the discussion. But I certainly don't troll, or post witty one liners just to get my karma up. A pay site would at least allow me in, but I don't know anyone here, and no one here knows who I am, so I wouldn't know how to get an invite.