Here's an interesting hypothetical situation for you. Any similarities to any real-life situation is purely coincidental.
Imagine a shared computer. Imagine that while making a backup of some files, you run across a stash of porn that somebody tried to hide, thinking it to be inaccessible. Imagine that this porn is… rather out there (and imagine that you've been exposed to some rather outre stuff as it is).
What the hell do you do, and how can you keep a straight face when meeting the owner of said files?