What seems like a long time ago, I was working at a place that used Linux, but not really any Linux experts. They had backup scripts that assumed (and did not check) that you would connect an external drive. If you didn't, the script would gladly copy files to /mnt/usbdrive, and if the server was full enough, backing up itself to itself would fill the drive and bad things would then happen.

There was no email notification if the backup completed or failed, or even started to run. There was no notification of how long it took, how much data was backed up, etc.

There were plenty of incidents of data loss.