This is my biggest "pet-peeve". It seriously pisses me off! What makes it worse, in Iowa, half the time there ARE NO CARS in the lane to the right. They're just retarded and drive in the left lane.
Just a note - not sure if it is the case but the downvotes are likely due to your use of 'retarded'. Outside of the US, using it in a negative context as you have here is considered offensive.