Agreed, but there is always a slim chance, if you have been excessive and careless when applying skins with a solution, that you may trigger one of the moisture detectors via a stray drop or two... thus voiding warranty if they check the detectors...
I did this on my 3G, but never had a problem with the phone, so never came into play for me. Did bug the hell out of me for 6 months until the warranty period was up!