If you look at the reviews at IMDB you will see something strange. Most of the reviews are either 1 or 10 stars. I feel like some kind of gaming of the IMDB ratings is happening.
That's not gaming. If a movie is rated 4 stars on IMDB but you think it should be 5, you won't rate it 5, you'll rate it 10 because that pulls the average closer to 5. Likewise, if it's rated 5 stars but you think it should be 4, you might rate it 1.