Yeah. Some good responses here. I have decided, after many years of experimenting with various gestures, that non-responsiveness is best. The people that do these ridiculous things from their car are in a state of altered reality...They are just passing through life as if it was a television program. They really don't expect any reaction or consequences to their actions and will just keep rolling along and letting the script unwind. I think it is dangerous to try to create even trivial deviations from their script (like throwing them the bird) in circumstances which you cannot fully control.