I remember reading something that had a funny perspective on this.

The main idea was that the joke used to be on the art critics that couldn't determine the difference between what was good art and what was just garbage. You could hang up paintings and then hang up the rag you used to clean the brushes and the critics would swoon over both.

At some point the artists themselves began mistaking the nonsense as art which is how you wind up with this: http://www.vice.com/en_uk/read/im-sick-of-pretending-i-dont-...