Hey pugnax ... send a friend request via xbl ... I'll go to live.com and accept. Once you do, go to # 22 in my MW3 vault and you'll get a very direct answer to the question you posed earlier, "What is it that they do to get banned?" I just caught the guy a few minutes ago. He was running his mouth as the lobby was loading, had a 1.32 kdr ... and goes 41-0. I thought to myself, "BS" (mostly because of something I won't say here) "No way."
Sure enough, a review of the game helped me confirm something I noticed during the match. He ran his mouth afterward and, as I was turning my mic on to respond to his request to show others how to play so good, he left the lobby.
THAT is how they do things to get banned.