"Curtis broke it"
I am routinely put on beta teams at my employer with the instructions "Hey, Curtis. See if you can break this". And I do. Because the guys doing the programming don't actually use the software daily.
To this day, there's one dev who has stated that under no circumstances am I allowed to "test" his software. Interestingly, whenever he says that, upper management then pulls him off whatever project he's working on.