I had the very unpleasant and unfortunate experience of encountering a dirty old perv this afternoon.
My car was parked in a dead end road and I saw this odd guy but didn't make a fuss and just got into the car and locked the doors just in case. I had to reverse out of the street so I manouvered my car around and I caught a glimpse of a sudden movement coming from his direction and, yep he was touching himself in broad daylight. It was disgusting but I pretended not to have seen anything and just reversed out onto the main road. I then noticed that he was still staring but I just drove away with no reaction whatsoever.
I've heard many stories like this but never actually experienced it myself, and it's really quite shocking.