>To be honest, I rarely have trouble with motorists, and when I do it tends to be pretty benign.

Me too. I think I get in far more road rage incidents as a driver than as a cyclist. When you're a motorist you're a real threat to people, their cars etc. As a cyclist, you're a mere curiosity, and occasionally the object of ridicule, or a minor nuisance.

The one I really hate is as you describe: head down, in your own world, and a car comes past and beeps. Hard not to get aggro then.

Steve