I disagree here. Netflix's system is a recommendation engine and not a rating engine. Yes, you are correct that a lot of morons misuse the 5 star system, only voting 1 or 5. However, a lot of people also use stuff n the middle. I think for recommendations you could get away with three levels.
0-2 can all be summarized as bad/didn't like. For recommendations, I don't see a lot of value in differentiating between complete garbage and bad stuff I don't want to watch. That could all be boiled down into thumbs down.
However, 3-5 has more granularity than just liking something. There are things I like and will watch, but am not too excited about. Then there are things I really liked and I would like actively recommended to me. I think you need at least thumbs up and two thumbs up for this.
This seems like it is going to result in even shittier recommendations.