My favourite in that regard is an anecdote shared by a customer; he said one of their techs had discovered (luckily in time) that the long-running automated backup script on a small, but important server wrote the backup volume to...
I can tell you since I work support for a backup product.
Lot of people think that naming a folder on a local drive "Disaster Recovery" counts as having an offsite Disaster Recovery copy of backups. The number of large corporations whose backups are in the hands of such people is frightening.
...RAM.