What makes me mad is that the person who sits in the left lane for 10 miles while I have my bright lights on and finally they move over and give you a look like "WTF". I would feel a lot better if they knew why I was messing with them. I'd like to have a digital sign in my back window that could display a little message.
I've seen sun visors on trucks that read "Get Over" with an arrow to the right when viewed thru the rearview mirror, like the "ambulance" ones.