I ran into problems with wikipedia during the recent elections in my state. Wikipedia was not my first stop in gathering information on candidates, but I did go there after forming some initial conclusions to see if the masses had noted anything I had missed in the governor's race. The incumbent surprisingly had, despite having worked in the state for years (and despite my having seen at least a couple of positive things in the news) not ever done anything good. The article was well sourced, but it was entirely negative. I will grant you that politics corrupts, but it seemed a bit off. When I got to the challenger's wikipedia page, I discovered that he had never done anything bad (or marginally negative even), only good. There are theoretically moderating folks involved in each area of wikipedia, so it was surprising that the pages (and their history for some time) were as they were. Others are noting that their edits are being rejected. I don't know much about this, but it would appear likely given this one example.
All the challenger's efforts (or his supporters') to "fix" the wikipedia entries relevant to the election were for naught (I guess not many people take wikipedia seriously). The incumbent ended up winning despite apparently having a challenger with a staff dedicated to manipulating popular websites.