Yeah, I guess runners are a bit nuts... I don't know the area that the race was being held in, but I'm guessing it's no run in the park. I really want to do the Wall of China Marathon one day. It sounds absolutely hard core. I find that pretty appealing :-p.
You do have a very good point that running is bad for people. I know that running is absolutely hideous for people's bodies. I haven't found anything else that gives me the same sort of buzz exercise wise though. Crossfit is pretty good but not quite the same. My PT reckons that running appeals to people with addictive tendencies. I can understand this. It's the whole buzz after a really hard session, but also a massive sense of achievement when you finish a set number of kms. So many times you just want to stop, but you finish anyway, it's kind of fulfilling. Definitely best in moderation though to avoid injury. All runners I know are in 1 of 3 states, not injured and running well, injured and not running, or running after returning from injury :-p.