I was told this story years ago by those who were supposedly involved. I worked for the company concerned, but I'm not sure if it makes the story truer or not. In any case, it's a fun story with a subtle moral.
There was an IT department in a big company who were installing servers in an older building that didn't have dedicated server rooms or closets. Because there was nowhere else to put it, they installed a server in an office. The server was a typical innocuous beige box.
After a few weeks, there were reports of trouble in the building. Fairly regularly, e-mail and other services would go down for five minutes at about the same time of day. The IT department investigated. They checked the server configurations, but the configurations weren't to blame. They checked the cabling, but that was just fine. They checked network cards and routers, but everything seemed to be working as expected. During the whole investigation, the network kept on going down at around 10:30am for about 5 minutes, but there seemed to be no hardware or software cause.
In desperation, the IT department posted someone to sit by the server all day to watch what happened.
At about 10:30am, a secretary filled an electric kettle with water. She walked into the office, unplugged the server, and plugged in her kettle. She made herself and her boss a nice pot of tea. When the tea was brewing, she unplugged the kettle and plugged the server back in. She then went to enjoy her break and have her cup of tea.
So the mystery was solved. The IT department put a notice on the server plug not to unplug it and identified the server as a server. The secretary found another, less convenient place to plug in her kettle, and the world moved on.
I was told this story by the IT department. In their telling, the villain of the piece was the secretary, who they thought should have known better. At the time, I accepted this and laughed with them. Now, I disagree. In my view, the villain was the IT department and the innocent party was the secretary.
No one told the secretary that the server was important; it wasn't marked in any way. She wasn't a technical person and she had no way of knowing what the box was or what it did. Because of the age of the building, the server was in an office instead of in a server closet, so there were lots of non-technical people in the area near the server. The IT department did know what the server was, and they knew that there were non-technical people around, but they chose not to mark the server or communicate to anyone what it was or how important it was to keep it plugged in.
Bottom line: don't blame people for not being psychic - it's your responsibility to communicate.