This is an excellent point. I've always wondered a little why Blizzard didn't build a reputation system into LFD. Yes, it could be abused, especially if they didn't design it well, but it could have made a massive difference. Heck, League of Legends recently introduced a "positive-feedback only" system that has apparently been very successful. (Given Blizzard's lackluster management of the kick feature, I'm not sure I'd want to trust them with implementing a negative reputation system.)