When I was working at the library at the U of MN campus, I saw a couple in a small dusty desk set up on the 8th floor. They left quickly and when I got to the location (I was trying to be discrete), they had left her underwear and a new date and name pairing on the "Sex in the Stacks is awesome" graffitti.

Sadly, that was the only time that I ever saw anything remotely like that in the library. Most of the stories were about the creepy tattooed guy that came every day and tried to make conversation.

I was later fired after turning on a light with a switch that was taped up. It blew up and the library had to be evacuated in order to avoid mercury poisoning.