Not on the PC... because you actually get banned for being a dick. Some kick you for swearing, which I think is a bit too much but gets the point across.
On Live, since all you get is a lower star rating... although I don't think that feedback system even works.
They say "play with friends"... except I don't know anyone who plays Halo 3 or CoD4 really. And neither game does co-op (well), so that's not even an option.
Now, if MS ripped off Steam and let people join groups and then join games that people in the group are playing... that'd be genius.