I don't mind if people drive in the left lane as long as it's clear no one needs to pass them. It's dangerous to pass on the right side of a vehicle, because there's a larger blind spot--if they suddenly decide to move over to the right, there's a good chance they wouldn't see you and would hit you. I always pass such people as fast as I can. *shudder*

Of course, all rules are off if you have more than two lanes. Lol.