As others have alluded to, there is actually a sociological theory called diffusion of responsibilty. It basically states that the more people there are who witness a crime, the less there are who are likely to do anything about it. Why? Because everyone assumes that someone else is going to do something about it, so therefore they don't bother. Since I learned about that, I have tried to go out of my way to be the one that helps or reports something if the situation arises. Actually, the situation hasn't really arisen, short of the power and or Internet going out an calling in to report it even if others probably already have, but the general principle is, I'd make sure I'd try to help (at least by calling the police) if I ever needed to. See the famous example of the woman in NYC who was killed in broad daylight while everyone stood around and watched. Kitty Genoves, I think.