dawn to dusk: That's a good idea in theory, but I've seen problems with it in other games where dickwads will spam you with invites just to piss you off, or, even worse in some games, the invite spam will actually get in the way of the game (covering stuff up, etc) and so some people would do it just to screw you up. I remember one online chess site that this was notoriously bad on; people would spam draw offers when they were losing, but you were short on time, and then there would be all this crap on the board in your way slowing you down in the last few seconds.