I must say that the original post gets me as well, you may well move over when it is safe to do so but if I am in the outside lane I am generally doing 80.
It may not be the legal limit but no copper will pull you over for it and generally that is the speed that the lane moves at. By sitting there doing 70 all you are going to do is irritate me, causing me to lose concentration on driving, maybe making me drive more erratically/aggressively and that could lead to more accidents.
If I had someone bearing down on me I would try and find the nearest gap and let them through, even if that means speading up a little bit.
IMHO a lot of accidents are caused by frustration of other drivers, if everyone was a little more observant and considerate instead of doing what they feel is right for them then the roads would be a better and safer place.