Maybe the "genius", if it can be called that was FB only allowing likes, rather than dislikes. You have to really agree with something to like it, as the default is to not react, and when you do react, most energy is to disapprove of something (for example, negative feedback, online reviews, etc.), so if someone gives something positive feedback it must have nonmarginal significance.

That said, the conclusions are very much expected. If i know what you like, i can know what kind of person you might be.