Although such "user errors" can be funny because they are so unexpected, we are in the business of designing systems and software to fit the users' tasks and characteristics. We *should not* be ridiculing users under any circumstances, no matter how stupid we may privately think that some of their mistakes are. To me, the funniest thing about such stories is what they reveal about our own expectations as designers.
[stuff deleted] ... I agree. It has always been made apparent to me that if a user makes a mistake, that's either a system's or its documentation's fault. I would hardly expect that a HCI newsgroup would need it pointed out to them. But then I've never really expected my HCI sympathy from a network based on Unix... :-)