Actually cheaters are banned every week (if not every day).
there is an engine detection on this site, it works well.
If you have a suspicion, use the 'report abuse' link at the bottom of all chess.com pages. (and keep in mind that maybe they just outplayed you :P).
Alright, that's all I have to say about that... oh and chess is like a box of chocolates... too much and you get fat!
I'm sick of cheaters on chess.com. Now and then I get beaten by some guys 300 or more points below me, not taking advantage of my blunders but outplaying me tactically and strategically on my good day. Come on people, that really sucks and it's getting on my nerves. On playchess.com cheaters are constantly detected when using computer assistance and sanctioned by deleting his/her elo points but on this site - never. Someone should do something about it...