Couple of thoughts and question for a moderator:
1. I find that "taking the lane" and using a mirror compliment each other, particularly when doing so involves slowing a motorist. If I'm going to be buzzed or worse, I'd like to know before it happens. I find it hard to believe that someone without a mirror can know he is about to be passed at 3 inches versus 3 feet. "I turn my head and look at every car before it passes me", or "my calibrated ears have exceptional directional sensitivity"?
2. Is it a coincidence that the A&S posters who most adamently espouse an "I don't need a mirror" attitude also most frequently report experiencing drama and close-calls with motorists (or JAM's, asshats, cagers, jerks, etc.)?
Moderator question (and for others as well) -- this is turning into the helmet thread and I created the "do you use a mirror" poll -- would it be worth combining the two and/or turning this thread into a sticky?