What if the act of telling people in the front half caused a stampede, which trampled five people to death, knocked a candle over, and burned the whole theatre down?

The thing about bank runs is that if everyone, everywhere thinks there's a bank run happening, this will actually cause the financial system to collapse. It's a self-fulfilling prophecy.

But if most people don't think a bank run is happening, then the system can weather a few bad banks popping.