This is quite ancient case. Mircea Hrubaru from Constanta (Romania) got banned in February 2009 from Chess.com, because he was found to be cheating. We cannot say whether he did it deliberately or by mistake, or he just came to conclusion, looking at top rated players (altogether mostly cheaters), that no-computer rule is not obligatory, but the output was quite strict and clear. Needles to say, he learned from it and became member of
FICGS, minor playing site, where engines are allowed.
Interesting things followed then, however. First, the member who reported him (Costelus) got fired from
Team Romania and then
Romana Chisu, the superadmin of Team Romania and chess journalist, opened thread in forums called
Petition for MirceaH, where clique of naive Romanian members tried to persuade staff to revoke the ban. It is worthy to read.