It can happen to anyone, at any time. Even professionals.

"I used to backup the data from that server every week, on another host. But last week, I needed some space for a specific application. And I temporarely deleted the backup. 2 days later, the disk died. And that host was always backuped for 5 years before. Call it Murphy's law or voodoo, but it really, really, really sucks."

You, reading this now. Yes, you. What would you lose if the hard-drive in the computer you are using now never span up tomorrow? Anything important/sentimental?
Never trust data to one hard drive. They die regularly randomly. (If you can say that). I'll repeat that: Don't trust hard drives.

A clever person said: "There are 2 types of people in the world. Those that have lost data, and those that will."

I suppose that there is one benefit to Open Source software - the source code to his FTP server can be found in many places. I use ProFTPd or vsftpd however.

You can always use this online backup service to make sure that your files are backed up.