In comment threads to feminist blog posts in reaction to a particular xkcd comic, I've seen good reasons why certain people might be very pissed off when other people try to talk to them somewhere they cannot get away from, though they mostly apply to women being talked to by men.
I would always find people in aeroplanes less threatening than in trains. I wouldn't imagine the person in the next seat mugging me, for example, whereas I would imagine it on a train.
What do other people think of strangers on a plane versus on a train?
r/Fitness does a weekly "Moronic Monday", a judgment-free thread where people can ask questions that they would ordinarily feel embarrassed for not knowing the answer to. I thought this seemed like a useful thing to have here - after all, the concepts discussed on LessWrong are probably at least a little harder to grasp than those of weightlifting. Plus, I have a few stupid questions of my own, so it doesn't seem unreasonable that other people might as well.