I hate them the most because it's so POINTLESS. Why would you bash something you don't care about at all when all it does is ruin other people's fun? If you really like a show/series/whatever and are disappointed in plot twists or bad development or something, or you have some legitimate problem with a work (re: Twilight's portrayal of "romance") I can understand complaining, but what is the fucking point of going "lol I hate this" for no reason?