No computer "needs" a screen protector.
Strangely enough naysayers, during my first week of owning my new 27" iMac, I had my Macbook Air open in front of it while taking some files across, went to angle the Air screen back and the sharp corner edge has left a small but perceptible scratch lower centre. Up until that point, I had assumed the screen was glass, not softish plastic!
Do any of you guys use one. Also do Macbook Pros need them?