Today I went to lunch at the Sizzling Express on 18th and M. I held the door open for five people. I got zero "thank yous." One lady was even rude enough to not say "thank you," talk on a cell phone, and chew with her mouth open, all at the same time. The trifecta of douchebaggery.
Sample size of study: laughably small.
Yet, I certainly feel it accurately represents the attitude of the locals around here. (And I'm from Massachusetts, the American capitol of rudeness. Still, we at least say thank you when someone holds a door open for us.)