After posting on bumper stickers, there were two posts by Megan McArdle on aggressive DC drivers. The comments here and here were also on a rather surprisingly reasonale tone and not as shrill as I had expected. The posts were mainly on bikes vs. cars and there is a sense at which both bikers and cars can be at fault. Add to that the distractions of Ipods, cell phones (on both bikers and drivers) and it's a recipe for accidents.
Distractions also can be due to other things such as talking like I may have been doing on a close call yesterday doing a right turn but was not conscious of someone else beating me to it from the opposite site doing a LEFT turn into my lane. In Washington DC there are also a lot of circles (or round-abouts as we used to call them) which a lot of drivers are clueless on handling - especially being in the "right" lane (if there is one). And I agree with one comment who said that in DC there are some who believe it is god given right to drive any way they like. (They're probably lawyers or lobbyists or their spouses.)