I remember briefly reading about how Pandora classified music -- by getting people to analyze each song for different qualities (e.g. fast paced, melancholy, et

I remember briefly reading about how Pandora classified music -- by getting people to analyze each song for different qualities (e.g. fast paced, melancholy, etc. etc.), and that was a key part of their "recommendation engine." You could ask people "What did you like about this movie?" and they could tag various things they liked about it, e.g. "was smart," "cheesy humor" or "had Jennifer Lawrence." Heck, that sounds like something that might be worth building, a tag-based movie recommendation engine.