Should we have a question listing known false proofs, and other fallacies? Like an official FAQ version of 113? Then for all instances of questions like 389180, 388435 and so on, we can just redirect them and close it. Like Qiaochu says, duplicates of these are hard to search for, although we're sure they exist.
We could probably draw on http://en.wikipedia.org/wiki/Mathematical_fallacy, and other existing such collections.