Technically, everybody is supposed to drive in the right lane, and only use the left while actively passing a car. Of course, neither the slow group or the fast group actually abide by the law, and as a result they despise each other's existence. Riding somebody's bumper is a good way to get killed, especially when doing 75+ MPH. Since I like to think I have something to live for, I'll patiently wait back a few carlengths until the slower car has finished passing traffic in the right lane. 99 times out of 100, they will move over once they are complete, and both that driver and myself are free from the road rage.