Re: Old IT joke
Try explaining to the new Commanding Officer in a military unit why it is that the power-cut has affected his office (not operationally essential) and yet all the sockets and lights in IT's office are still functional.
The operational reasons of making sure the office, DC and path to the DC stay live are obvious, but the explanation is somewhat undermined when it's pointed out that your coffee machine is plugged into one of the "essential" sockets.