I live and ride mostly in Maine, where there is a lot less trafic than in LA, and also ride and drive sometimes in Boston. I think that the hostility increases with population density - my daughter has made the observation that in Boston, many of the cars seem to have the horn connected to the brake pedal - anything that causes them to slow is worthy of a honk. For honks, I usually wave to them - with all fingers. When a driver doing something stupid gets close enough to me, I hit it, usually with a fist. Gets their attention. This last happened a week or so ago, I was riding down a road, one lane, approaching an intersection where the lane splits into a RTO lane and an LTO lane - I am preparing to turn left, and am in the center of the lane - long line of cars waiting to turn right, nobody in the LTO lane. I am in the center of the lane, when a black mercedes honks at me, and passes on my left, only to cut across my front to get to the stopped RTO lane. I thump the back of his car with my fist as he passes in front of me. Sadly many of these drivers value their pieces of steel more than they do the safety of cyclists or other drivers.