I've seen lots of spammer types recommend Scribd, so once again a good idea is having issues.
It may or may not hit a legal wall. I look at the efforts EZineArticles and Squidoo have made lately to clean up. It wasn't so much the legal wall (for EZineArticles the bigger issue was people writing one article and "spinning" it into 10-20 articles). The big issue was that they were getting perceived as low quality spammer sites and that was going to kill them long term.
I think Scribd will be forced to clean things up for similar reasons if the lawyers don't stop them first.