I also think it depends on the person coming behind you. If it's someone going 80 and you're doing 75, I agree, especially if an opening is in view within a few cars.
But those real crazies that are whipping in and out and coming right up on you, I think you should try to let them over and just get them away from you. They are often young men (sorry guys) and often make sudden movements.
I tend to do the same thing. I will stay out of the left lane except for passing, and when I'm passing and somebody comes up on me, *if* I can safely get over without too much trouble, I will, and I will let them by. But if it'll just take me ten more seconds to get around the guy beside me, and then I can get over, I'll do it. And if somebody in the passing lane in front of me does the same thing, it's no big deal...I can wait the extra few seconds if it gives everybody a smoother drive. I drive a hard-used pickup truck with 137,000 miles on it and dodgy brakes anyway, so I don't tailgate.
The only exception to this is if somebody comes screaming up on my ass and parks four feet off my bumper. Tailgate me like that, and you'll get to see just how slow and wide I can make a '96 Ram. Drive like a sane human being, and there won't be any problems.
My mother (80 this May) is one of those "I paid my taxes so I can drive 55 in the left lane if I want" people, and the sad thing is, she taught me to drive. So 20+ years ago, I was motoring my little '76 Datsun B210 (curb weight: 1800 pounds) down the left lane of four-lane highways at 55 mph exactly, and couldn't quite figure out why everybody was flipping me off and tailgating me. It took a couple of years, and a few trips out onto Interstate highways, to finally get it through my head that driving slow in the left lane is BAD.
}:-)4