My initial impulse was to make a blog post setting out the thesis that the largest cause of aggressive driving are the passive aggressive drivers who clog-up the passing lane. They may be going close to the posted limit, but are far below the prevailing speed for that lane.
I decided, partly due to not being able to locate the print edition in the recycling bag, to find the online version. Once I got there, I perused the comments and changed my mind a bit about the post. The comments ran about 10:1, most drivers complaining about people who squat in the passing lane and a small minority of self-righteous pricks (guess which side I am on) who essentially say that they can be in any lane they want as long as they are at, or close to, the speed limit.
The problem is that it only takes one out of ten drivers to royally screw-up a highway. So often I have seen 1/2 to 1/4 mile-long traffic clogs caused by the concatenation of 2-3 slow cars blocking all three lanes. Around here (New England) the posted speed might be 65 (when it is 55 the lane speeds are pretty much the same FWIW). The leftmost lane will have a prevailing speed of 80, the middle 70 and the right 65. The clog happens because many citizens prefer to cruise in the middle lane to avoid traffic entering and exiting on the right. Then a motorist going 66 will pass (on the left) a driver in the middle going 65. The roads out here are usually pretty full, so a lot of traffic will pile-up behind the 66 MPH car while he takes a couple of minutes to pass. The delta speed in the left lane is 14 MPH and in the middle it is 5 MPH.
Oddly, the right lane is often quite empty and aggressive though it may be, I have passed traffic clogs consisting of hundreds of cars, by zooming along in the right-most lane.