How many of you pay a little *too* much attention to other cars on the road?

I drive mostly rural roads and small towns, and I find myself almost studying each car behind me and in front of me out of some irrational expectation of them doing something to piss me off. Not so much that I want to be ready to react to potential danger, as much as I just feel the need to categorize people into "crappy driver/decent driver" for future reference. Is it just me?