What's odd to me is how many people will do it once you're outside town. Driving to Flagstoff/Prescott/Sedona it seems like everyone is aware of this "rule". The second you get back into town everyone is back to driving like garbage.
Can I also throw in my personal pet peeve of people (usually on cell phones) changing lanes in front of me at a light only to go 10mph slower than the car they got out from behind. WTF is this about?