If you see someone doing something dangerous and the seem not to know it would you warn them? Do you have a responsibility to warn them?

Of course I don't warn people not to take drugs. Maybe because I believe they no the risks and have choosing to do so away. But would yank somebody back to the curb of it looked like they were about to get hit or if they weren't that close, scream to "look out!".

This comes up beause today I saw a guy cleaning his ear with an 8 inch long ear scrapper at his desk. Like most Japanese companies we don't have cubes and he sits on the aisle so the odds of him getting bumped in the elbow while doing that are not that low. In the position in which he was sitting people walked by within about 6 inches of his elbow.

I'm only sensitive to this particular issue because my dad once told me about his friend who was cleaning his ear, his wife came into the bathroom and when she opened the door, bumped his elbow destroying his ear forever.

I didn't warn my co−worker. I don't know him yet and I felt like I would be butting in. Of course if he loses his ear I'll probably feel like I should have said something.

What would you do?