You used to do a survey and rate movies on a five point scale: hate it, dont’t like it, indifferent, like it, love it. After going through several movies and shows, it got pretty good at making recommendations for stuff you would like. Now it’s just thumbs up or thumbs down. It’s useless.
I can't even recommend movies for me, though. But I like the idea of playing with a rating engine. But not enough to do the work. But maybe if someone had told me about it I might have tried it.