> They obviously determined that thumbs up/down either generated better training data or more training data. I'm guessing that the definition of "better" chang

> They obviously determined that thumbs up/down either generated better training data or more training data. I'm guessing that the definition of "better" changed at some point, perhaps when they went from 1-5 stars to +-1 thumbs. In Netflix's early years, I was confident that their classifier's goal was to predict my future rating for a given video. I.e., it was part of a larger system designed around my viewing pleasure. Around the time they switched to thumbs, I started suspecting the classifier was being used to manipulate me towards optimizing Netflix's profitability, instead of my viewing pleasure.