I spilled coffee on my screen,so who knows what liquid would've done to the touch screen,it's a touch screen you break that lol bye bye iPad lol
Liquid is a hazard only if it gets inside to the electronics... A screen protector won't do anything to protect against that.
It is funny that screen protection has migrated from the days of the Palms, and tablets, that used to use plastic screens, which would (and did) scratch easily, to hardened glass that is extremely scratch resistant (like sapphire watch crystals).
The glass that they use with these things is very tough... Sure it can get scratched, but not with normal use... If you are carrying it around in a pack with metal objects, and such - it could get scratched, but with minimal care, it will do fine. My iphone 4 has no protector, and I have no scratches, and I keep it in my pocket - slide it around on my desk at work, etc.. no special treatment, and its pristine when I clean it. Oh, and treated it that way for over a year now. My son has my old 3 Gs (2 years old) and he is a teenager, and so you KNOW he does not take of it, and the outside plastic case is all beat up, the glass is pristine with no scratches.
I do use a matte anti glare on the iPad, because I actually like the tactile touch feedback I get, and i like not having reflections in the glass. But, I don't use it for screen protection. But, like everything designed to "protect" there will always be those that insist something was saved from an accident...
I like the saying above about the fishing accessories - although I admit I have fallen to that as well, I guess much comes due to fear of having to pay something now to prevent a more expensive payment to replace later on... But like the product warranties that many of us pay for - the vast majority never need to use them, and that is why companies push them - they are VERY profitable... I guess screen protectors are too....