A few weeks ago I observed a probably off-topic but non-spam question quickly gathering delete votes as spam, and then someone actually maliciously edited the question, overwriting it with "spam spam spam..." to prevent the question from even being read. I don't see that there's a "history" tab where one can view previous revisions.
Then it struck me that someone could go back and edit his answers (or, with enough rep, any good answer) after a few days had passed and the questions were off the radar, turning them into obfuscated gibberish. While eventually those would gather downvotes, it takes five downvotes to erase an upvote; and in any case the shared knowledge is lost.
What's to prevent this if enough members turn to the dark side? Or am I just being overly paranoid about something that has little likelihood of occurring?