What about that congressman who thought that having too many military personnel in Guam would cause the island to tip over?
When I used to work at the librarian, a librarian told us this story through tears of laughter. She had a customer come up to her *totally* infuriated. "I've been asking for help for ten minutes and nobody has come to help me! I'm almost out of computer time!" The librarian was puzzled, since she'd been right at the desk the whole time and the woman hadn't come up to the desk at all. "I was right here and I didn't see you get up. How were you asking for help?" "I was pushing that F1 key over and over and nobody came!" I would totally think this was an urban legend except that the librarian told me right after it happened, so I guess some people really do make that mistake!
But most of my exchanges that make my brain hurt are with my 4-year-old. She has a talent for asking the kind of questions that force me to answer, "Uh... I don't know. I will have to ask Papa/look that up and get back to you." Good thing I'm married to an engineer.