4.) Making a barrier with fellow slow drivers
If people want to drive below the speed limit, that's fine -- really. However, do you think anyone's ever noticed when there's no traffic in front of them, then looked in the rear-view mirror (of course not)
and noticed that there's a mile's worth of cars behind them, because they're going 5 mph under the speed limit, next to someone who's going 5 mph under the speed limit, next to someone who's going 5.5 mph under the speed limit? (License plates reading New York, British Columbia, and Minnesota, respectively.) If you want to make friends, don't be ignorant or inconsiderate.