Hmm, those numbers are definitely too big to be influenced by anyone's network. Judging from the other top-ranked films, it looks as if IMDB's userbase is in the middle of changing.

I don't think they need to game the system. The lukewarm or negative reviews on RottenTomatoes are being bombarded with genuine fanboy vitriol. (Many of the commenters, at least on the first page of comments, have joining dates that suggest they have been on RT for a while) http://www.rottentomatoes.com/m/the_dark_knight/?critic=crea... It is quite amusing in a sad way actually, seeing them trash the likes of David Denby and Joe Morgenstern.

To be fair, those reviews were both fairly terrible. Fanboyism is never justified, in my opinion, but I agree with the respondants' sentiments.