There are about a million variations of drivers that piss me off on the highway. Right near the top of the list is people who use me as a pace car. They come out of nowhere and suddenly they're on your back bumper.
And they stay there.
You speed up and they speed up. You slow down and they slow down. Apparently they love your company. That might be nice if they weren't so fucking intrustive. I've got some advice for dickheads who do this:
Either back off or overtake. Don't just sit there. My back seat is already full, I don't want you there too.