It's probably just not that hot of a solution, believe it or not. The recommendation engine should be able to make much better associations between movies, without even being able to describe what those associations are. Looking at features like genre, director, actor etc, is like a spam filter looking for specific spammy words. As soon as the spammers start saying "p3n1s" instead or Eddy Murphy starts making family movies, it falls apart. Check out http://karmatics.com/docs/evolution-and-wisdom-of-crowds.htm... (scroll down to "3. Recommendation Systems" for the relevant part) for an explanation.