I don't understand why anyone would join a crowd in the first place, no matter what the reason for the crowd gathering. If I ever accidentally end up in a forming crowd, I get out of there, fast, before anything bad happens. Sometimes it is difficult - for example, we have season tickets to our NHL hockey team, and there is always a crowd bottleneck getting into the arena doors. In that case, we go to the farthest outside line, and once inside, go to the farthest and least used (read: "least convenient") metal scanning location. It's too bad they recently put up those scanners. It really bottlenecks things and backs up large crowds. They don't do any good. Just a "feel good" thing for some people.