Completely not needed. I don't have a mark on mine after several drops and my wife's has bounced around her purse for over a year without a scratch. Gorilla Glass was great and I can only imagine how awesome Gorilla Glass 2 is.
I'm sorry but I don't believe this. Clean your screen with a soft cloth, turn it off, and hold it at an angle. I guarantee you will see blemishes in the screen.