Was told this story by a work colleague...
He was working in Germany for a telco and they were upgrading the redundant systems for a couple of data centres (electrics, hardware, software etc). The demo was set for the CIO to come and see it all working and properly test it by killing grid power supply to the data centre by throwing the breakers, simulating a power outage.
The day came, with great ceremony the breakers were pulled by him, grid power ceased and lo and behold everything worked as it needed to. Generators generated, UPSs hummed, servers shut down in a controlled and graceful manner. Seeing the success the CIO then said (in German of course), "Excellent, well done. Well, better get the power back then...." and threw the breakers back before anyone could stop him, missing several hours of carefully prepared procedure to move back to normal operation in a single swoop. The surge of current took out enough power hardware (generators, switches, UPS etc) that it was days and days before the data centre was back up and running.