Since I'm tired of poeple asking for rank hacks, I'm just going to clear the air on the issue.
The reason that there are no rank hacks for Call of Duty Black Ops, is because (unlike other COD's) your players stats are kept on a server. Not on your computer (which is why there are rank hacks for previous COD's).
I hope that this resolves all of the questions on why there are no rank hacks for Call of Duty Black Ops.