People who don't anticipate or prepare for what's ahead. As far as they're concerned the only car to worry about is the one immediately in front of them :dozey:
People who stop at a roundabout when they don't need to (anticipation again!) :dozey:
People who religiously stick to the lower speed limits but not the higher ones (pootling along the am commute along a 60mph route at 40 drives me nuts!!) :dozey: