I forgot to answer your first question. We released a new prediction engine a few months ago (http://blog.netflix.com/2009/05/more-accurate-star-predictions.htm

I forgot to answer your first question. We released a new prediction engine a few months ago (http://blog.netflix.com/2009/05/more-accurate-star-predictions.html http://blog.netflix.com/2009/05/more-accurate-star-predictio...)... I think it's safe to assume that we wouldn't have used new algorithm(s) if they didn't work well on our ~3B ratings.