(This might seem like it's on the cusp of being relevant, but I think it's appropriate, especially given that voting on things applies to lots of webapps, not least the SO family)
I just discovered the following, from IMDB:
Weighted Average Ratings
IMDb publishes weighted vote averages rather than raw data averages. Various filters are applied to the raw data in order to eliminate and reduce attempts at 'vote stuffing' by individuals more interested in changing the current rating of a movie than giving their true opinion of it.
The exact methods we use will not be disclosed. This should ensure that the policy remains effective. The result is a more accurate vote average.
Does anyone have any idea what that means, in more detail? Or any references to relevant material?