... based on the other torrents that people seed who also seed that torrents you leeched?

If many people that seed some movie I leech also seed others, or if the same person that seeds a few movies I leech also seeds others, it seems likely that I'd like those movies too.

This would basically be "People who liked this also liked ..." but it would work for everything (I'm not aware of any site that shows what movies I might like based on what books and music I like, even though there must be some corelation) and it would be hard to spam, you'd have influence only to the extent you support the torrent network.