Some companies have threatened lawsuits against people who left bad reviews online. Writing a bad review is a powerful form of catharsis. You spent money on a good or service and had a negative experience, so you do the only thing you can: try to warn others.
What these reviews lack in helpfulness they make up for in gleeful goofiness. For its part, Amazon hasn't tried to dissuade this phenomenon, as these self-generating memes can actually increase sales. For example, when an unexceptional graphic T-shirt featuring three howling wolves caught the ire of the sarcastic community in 2008, it went on to become one of the top selling pieces of apparel on Amazon that year.