If you've ever watched the TV show House, you will know that the main character (a doctor) has a rule that you never believe a patient, because "everybody lies". It's a very dark view of the world.
I can relate.
I've had friends ask me to take a look at computers, and while not everyone lies, I do find that many of them do. I imagine for a full-time tech support professional, it is doubly so. For example, if you spilled coffee on the computer, please don't tell me you dropped it. If you dropped it, don't tell me it just stopped working.
Any of my former IT students run in to this?