Any confirmation that the "X's" are actually getting clicked? Maybe it's just me, but I think that most people aren't retarded enough to look at an advertisement, decide they don't want it, and then take the time to complain about it. But then again, i'm not most people.
Well maybe most people don't need to click it...only a few in order to get noticed/flagged or whatever. Like how most people don't click on ads, but we still get them out of the thousands and thousands of impressions we get...so surely some people are x'ing those ads.