One of the first things they told me on my first day as an operator in the data-center of a big phone company was: "Remember, in Unix it is not Ctrl + C, Ctrl + V but Ctrl + Insert, Shift + Insert".

One night, in my second week there, I saw some errors on the console coming from a billing process that was running since a couple of days before. I called the on-call engineer in charge of that process and he asked me if I could copy-paste the errors and email them to him...

That month, about 2 million clients received the bills one day too late.