I always thought this was accidental, but I guess I'll never know.
I once lived in a downtown penthouse apartment atop a six story building. Because I was on the roof, I could see into a light-well between my building and the adjacent one. I could, in fact, see into the bedroom of a guy in his teens two floors below -- not very far in, but his bed was close enough to the window for me to see him when he was in it.
He was a very regular looking guy. I'd see him on the street with his friends (some girls, some guys), see him playing baseball in the park, or shooting hoops at a nearby playrgound. I also watched him jerk off about a zillion times over the course of a few years. He loved is nipples and his ass, both of which he gave a lot of attention.
One day he was upside down on the bed, hammering away, and looked up and saw me. BLANG! Down came the blinds, never to be raised again.