I've also seen a few of these over the years.
We ran a server, which was explicitly only for backups of work, but had a few people save their only copies of stuff to it, which was fine until multiple disks in a RAID 5 array died simultaneously...
The worst was someone contacting me to ask whether I could help with a hard disk problem. They were due to finish their PhD in a few weeks, and had _everything_ stored on the hard disk in the PC that they'd been using for the last three years or so. No backups, no copies of the original data or anything. They'd arrived one morning to find that the PC had stopped working overnight and nothing they could do could coax anything useful out of the disk. Luckily after a week of work on the drive, I did manage to recover the majority of their work.