Read the GPL carefully. In addition to the one in it, you are supposed to put in another disclaimer of warranty. IANAL, but I suspect that if you didn't someone could come up to you and say, Well by section 5 I decided that I didn't want to accept your stupid terms, including your lousy disclaimer, and so I am suing you within an inch of your miserable existence!

I don't know whether this was possible, but the FSF certainly thought there was some issue or they wouldn't have put in those instructions...