As someone who does a lot of driving (my commute is an hour each way, most of that is highway), this is one of those bad driver things that I see all the time that drives me nuts.
If it's been a while since you took drivers' ed, let me remind you: THE LEFT LANE IS FOR PASSING. That's not just my opinion, it's the law. And it's what makes the most logical sense, so really, there's no reason for you to drive slowly in the left lane. Further, even if you are already driving above the speed limit, if you are in the left lane and there are other drivers who want to pass you, YOU MUST MOVE OVER. You don't have to like it, but you do have to do it.
Slow drivers in the left lane are actually very dangerous. It's not up to you to slow someone down. Just move over and let them pass. And if you don't, you could get a ticket!
YES! Score one for the FHP! They're going to start issuing tickets to left-lane hogs! WOOO!
Here's WHY it's dangerous to drive slowly in the left lane: