I used to play backgammon on yahoo games. But the thing that sucks, is that people tend to quit when they are losing. I dont know if that is still a problem, as its been a while since ive been there.
i do know that some of the new PS2 games that you can play online now have a rating system, regarding the reliability of an online opponent. Maybe by now, yahoo has done something like that.
Only speculation though,
Jonathan