Twitter
That's one of the head guys at Infinity Ward.. - They are looking at the leader boards and game footage.. anybody who rank hacks actually has a high chance of getting banned. I got banned from Black Ops for running a fast exp server so this is a waiting game to see if they actually do ban..
Although, what I did read on his Twitter, is that I think they are only banning you from the leader boards. This means steam won't ban you for rank hacking, but Infinity Ward will. Meaning you can still play the game, just never rank on the leader boards again..
Hope this helps. :3