There was an incident at Pixar that a runaway rm ate most of the Toy Story 2 movie.   The only thing that saved them was an employee had their own copy on a machine at home.

We never lost the whole disk through one of these, but we did have a guy wipe out /etc/passwd one day.   Our password fields had an rfc-822ish user name in the gcos field, so it looked

something like:

ron::51:50:Ronald Natalie <ron>:/sys1/ron:

Well, one of our users decided to grep for a user (alas while root) with the command

   grep <howard> /etc/passwd