Where I live has a lot of retirees (Yikes, I'm one of them!!) and what I find is many of them have no spatial awareness of their cars, so they don't realize their side mirror is about to clip you. And they also have a morbid fear of ever crossing the center line, so they won't give you space. Call me silly or superstitious, but when someone is kind to me when I'm on the bike, I give 'em 2X the love -- I wave, smile or nod.
Making sure I keep a positive balance in the karma department...