If it is really obvious, then it is not a real problem, because we can delete the stuff quite quickly.
Files like "eminem-full-cd" will not get very old in here. The office or windows illegal copies are easily found as well.
The real challenge are the e-books and pictures some people try to sell and which are plain and simple stolen from other authors.
Read here, why we delete that stuff asap!
I am currently thinking of a "signs of quality" sheet with a regarding PHP program, to get rid of these files before they could cause trouble. It should be possible to trigger some warning signs already on upload, like: did the merchant configure his layout first? If not, he maybe just abusing us... things like that could be a helpful indication!