I used to work for Loudcloud, an early dot-com hosting company. We used very expensive EMC Symmetrix storage for our DB tier. (Search the web for EMC Symmetrix 3830 if you want an idea what these beasts looked like.)

The Symmetrix had an EPO (Emergency Power Off) which was a red button mounted in a recessed area on the back of the cabinet, and was protected by a plastic lid. To perform an EPO, you had to lift the lid and hold the button down for 30 seconds or so.

One of our DC ops employees was moving a heavy server into a cage and accidentally bumped the corner of the server into the plastic lid. The plastic lid was forced inward and got jammed depressing the EPO button. Moments later the entire Symmetrix powered off.

Later that day, as the word got around, another DC ops employee in a different datacenter looked at the Symmetrix and curiosity got the better of him. He didn't see how it was possible for the plastic lid to get jammed. So he punched the lid with his hand. Moments later that Symmetrix went down too. :-(

We reported this design issue to EMC. A while later, a few of us were on a factory tour at EMC. They pointed out to us the "Loudcloud Stopper" work-around. It was a rubber stopper mounted next to the EPO button that prevented the plastic lid from being pressed inward.