I have some of the local "rocket scientists" pass me as close as they "safely" can and honk the horn when they are right beside me.
I'm not sure what they are thinking when they do this. Er, ah, bad choice of words. They can't be thinking.

Are they trying to scare me into riding on the sidewalk (illegal around here)? Or riding only on my neighborhood streets? Not a chance.
One moron did this to me last Saturday and I got his tag number and the color and make of the pickup truck. He had to stop at the next light. I almost caught up with him but he turned right just before I got there. I turned and saw him turn onto a deadend street. I turned onto the street and spotted the truck. He must have seen me following him and quickly ran into his house. I hung around riding back and forth in front of his house waiting for him to come out but he didn't.
Now I ride by his house whenever I go out. It's less than 1/2 mile from my house. He hasn't shown his face yet but I'll be waiting.
I wonder if he does this to all cyclists. His house is about a 1/2 block from a road that several cyclists (10-15 per day) use to get to a local riding/training area.