I see it constantly, not just cyclists but runners, walkers, you name it. I honestly believe that they just don't realize what they're doing. It simply doesn't occur to them that they're being rude, selfish or dangerous.

Sometimes, a cyclist will lose his cool and start shouting at people, lecturing, giving belligerent instructions on passing, ringing bells, anything that crosses his mind that other people are doing wrong in his opinion. It would be a nightmare to be that guy, even once. I try to just let it all slide - try, nobody's perfect all the time but I try not to let it get to me.