Years ago, a Melbourne university set up one of its very first PC labs. Some of us discovered that you could FTP anonymously to a PC while someone was using it. We didn't steal stuff or anything, but we would access A:. Most often than not the students didn't have a floppy in A: which would cause the message "Abort, Retry, Ignore" (or something like that). We would be looking across the room trying not to LOL to much, while they would scratch their head, trying to figure out what went wrong.