[bugra]

That is exactly why I generally prefer median-like average methods versus mean-like averages in these type of crowdsourced systems. Generally speaking, average votes are distributed evenly whereas the ratings on the edges are not. The movies that you gave as examples could be due to preference of voters for particular type of movies.

[AimHere]

I don't think it would make much odds for IMDB. Sure you'll maybe negate the overly high proportion of extreme votes, but I don't think that effect is large. I did once take the top films on IMDB and remove the extreme votes, and the effect was marginal - a few films shuffled a place or so. In exchange, if you use the median, you could have polarising films - like Twilight, having their ratings change markedly over time, as people decide to start warring over it and the numbers swamp the small number of ambivalents.

For your other point, there will be voting patterns for various demographics and certain groups of people prefer certain movies. But I think the phenomenon I'm describing is a bit too extreme to be merely a bunch of old women disproportionately taking a dislike to Ikiru and then rushing onto the internet to tell the world they hate it. It is the smallest demographic IMDB has, so it's not hurting the ratings of the films in general, it's just an oddity.