What about a dynamic environments... (Score 5, Interesting)

This completely reminded me of the opening of the London Millennium Bridge in London (crossing the Thames) were the bridge (nicknamed the Wobbly bridge) began to sway due to a few pedestrians who, by happenstance, inadvertently stepped in the same direction at the same time, causing a slight sway which on the rebound caused a few more people to step into the same direction, causing further swaying, increasing the effect w/ every oscillation. This effect is known as Synchronous Lateral Excitation. The funny thing is that each step, even several in synchrony, have negligible effects on bridge stress models... it was that this particular sway happened in such a way that forced more pedestrians on the bridge to step INTO the direction of the sway, continuing until most everyone on the bridge (up to 2,000 pedestrians) were contributing energy to the sway. The aforementioned is an instance of an unexpected design flaw due to inadequate modeling, and one can always come up w/ such instances, but these are meant to be learned and avoided... not repeated.