If you write a book that people read, and it's sold on Amazon, it might get one-star reviews from people that haven't even read it.

If you're an independent musician and you put your music on MySpace for all to hear, you'll probably get some wall posts telling you that you sound exactly like [insert popular band here], and that you lack originality, so you should stop trying to record music.

If you start making videos and putting them on YouTube, people will leave comments saying your videos suck and that you shouldn't waste your time making them. (And eventually, that comment thread will inevitably turn into a debate about religion, politics, or whether or not the U.S. government was behind 9/11.)

Critics are looking for enablers. Without the courage (or capacity) to create something of their own, they'd rather tell you to stop then take the chance themselves.