1) On a two-lane rural road where the speed limit is 55, you come across a car doing 50. You're doing 60, so you pass. You then come to a small town where the speed limit is 45, then 35, so you slow down accordingly. However, the car you passed seems to have only one speed regardless of the speed limit - 50 - so now this car is right on your tail.
2) Car passing you on the interstate decides it's more interesting to ride side-by-side with you for a while before moving on (kind of like your #1 driver).
3) You're going 75 in the left-hand lane of a 3-lane interstate. Car gets behind you for a while and you realize you shouldn't be there. But the car behind, instead of using the open middle lane, is content to stay behind you, so you hang out there for a minute to see what he does. When you finally move to the middle lane yourself, car that was behind you then zooms on.
4) Cars that DON'T MOVE OVER when you're merging onto the interstate, even though no one is blocking them from doing so.
5) The tailgater. Hey bozo, this isn't NASCAR; no need to draft me.