Well that's annoying. Seems like an example of Apple throwing a fit when a company makes a product to correct a potentially fatal problem with their devices (fragile screens).
I've had two iPhones (2G and 3GS) and have never used a screen protector. My 2G didn't have a case, and was dropped enough times to cause the black plastic piece at the bottom to come off. However, there were no blemishes on the screen.
My 3GS has an Incipio Feather, an incredibly lightweight case that doesn't protect the screen or provide any sort of bumper if the phone is dropped on its face. Still, no blemishes.
In short, I wouldn't consider this a fatal problem. Especially since the screen damage I've seen has all resulted in scratches or cracks. Anything strong enough to scratch glass is surely strong enough to scratch through plastic. And anything strong enough to crack the glass isn't going to be affected in the slightest by a piece of overpriced cellophane tape across the front of the phone.
However, the laptop covers seem justified. The palm rest on both my sister and monther's MacBooks are dingy.