Years ago, I worked in an investment bank and we had a programmer put a batch program into production that executed the following as a shell command:

  rm -rf foo /

It was supposed to be:

  rm -rf foo/

It didn't run as root, but still managed to wipe out all the business data files. What saved us was that the servers were configured with RAID 1 and before the start of the nightly batch cycle, the mirror was "split" and only one copy mounted.

So we just had to restore the missing files from the other half of the mirror to revert to the start of the batch window and rerun the entire night's jobs.