You gotta blame the "fans" that jump on rating their fav films, like alien vs. predator, with double accounts and stuff. Once a film has over 10,000 votes it offers quite a realistic rating on the film imo. Usually.
Need proof?
http://imdb.com/title/tt0443453/
That's just one but there are lots of examples like this. I used to take the ratings seriously, but that's a mistake.
Here's another:
http://imdb.com/title/tt0119654/
almost 70% for Men in Black? gimme a break
