What recommendation systems stand out as the most effective/relevant to you guys? These can be largely explicit feedback based systems (ie Netflix), implicit feedback based (ie Amazon), social graph based, etc.<p>Not looking for RMSE metrics or traffic driving numbers as much as subjective personal opinions.
Personally, I find Netflix does the best job and is easily worth the rating-entry time investment required.<p>It's not because of the content they show me, but rather because of the accuracy of their "predicted star rating" metric. Netflix showing me a broad spectrum of content I can immediately parse through by looking at predicted ratings combined with all the other standard quality metrics I look for has led me to find an immense wealth of content I never would have guessed I'd like.