Gah. Tailgaiting is such a pet peeve of mine. If I'm in the right lane (aka the slow lane) and someone is tailgating me, I'm likely to slow down further because it pisses me off: just move to the left if you want to speed. I typically go ~5 miles over the speed limit. If I'm in the left lane (aka the passing lane) and I see that someone behind me is speeding up, I try to move to the right or middle lane fairly quickly to get out of the way.

I also hate when people go 5-10 miles below the speed limit without reason (ie weather); however, I also try not to tailgate either because I try to stay clear should the person slam on breaks.