What's nifty about the mechanism is that it doesn't, at least for now and according to the article, require the ever so difficult sentiment analysis. You have to explicitly "like" something or check in. Some users will have fun abusing this, but not so much more than some researchers abuse machine learning/nlp who complicate their living by putting too many constraints on a machine intelligence task. (Don't get me wrong, I love machine learning/nlp; it just doesn't have to be more complicated than it already is.)