Now that BO2 isn't the main CoD version, a lot of people are dicking around and hacking, boosting, and cheating so there's a long list of cases to review. I can't speak for others, but over a two hour session, I run across maybe 12 people boosting on the PS3 and report each one, so it all adds up. I've been told that they do investigate each case.
I'm not sure if they just ban the IP or the account, though it was be great to be able to weed out everyone that hacks/cheats. The sad thing is that I saw a video on youtube where a guy rants about finding a booster racking up 80 kills in minutes, and the comments were saying "You're just mad cuz he's better than you" "It's just a game, let them play how they want" and slew of racial slurs since the ranter had a hispanic accent.