But, just like in Linux, the person would probably try to install some freeware or shareware program onto it and wouldn't know that it couldn't be done, much less how it is done.
I have a real problem with Windows users who don't know how to back up files. In this respect OSX is a nightmare because, as an administrator, you have to change permissions on files and directories to be able to back them up. Now I usually just tell all my user friends to get a 1G mem stick, and when they have filled it up, to burn it onto a CDR and keep only the essentials on the mem stick after removing most of the files (OSX, XP and Linux).