Most computer users quickly learn the importance of backing up data, but you'd be surprised...
I recall an episode of "Sex and the City" where Carrie has a hard disk crash on her Macintosh Powerbook and discovers that no one ever told her to back up her data.
A friend of mine had a similar experience some years back. He called to ask what a "Drive C unusable" error message was, as that's what appeared on his screen when he tried to boot up his computer.
What it meant was that his hard disk had crashed. He asked if I'd install a new one for him and I agreed.
I asked if his data was backed up, and he said not to worry because he had good backup software. So off I went to pay him a visit, stopping at the store to pick up a new drive for him.
I got to his house and installed the drive. Then I said, "Give me your backups and we'll get your data restored to the drive."
He handed me an unopened copy of a Windows backup program. "Here you go" he said. "The salesman said we'd need this eventually."
He thought that simply owning backup software somehow protected his data. No one had every explained to him that he had to install the program on his computer and run it.
I'm almost paranoid when it comes to backing up my data. I do a daily backup to a removable hard disk and to my iMac disc on the Apple Internet Server. Even if my house burns down, I can still recover my data from my iMac account as it's sitting on a secure site on the Internet.
I've even started backing up my recording of client sessions. These days most people record audio onto a computer hard disk and then burn a copy of the recording to CD using a process audio professionals call "bouncing."
This works great for most purposes (I use it to create my master recordings), but as it can take 15 minutes to "bounce" a recording of a 30 minute hypnotic session, a hypnotist can't record that way if you want to do a real-time recording of a session that you give to a client.
Real-time CD burners exist but judging by my conversations with Tech Support, a lot of people are having trouble. It seems that some of the companies that make the CD-R blank disc media have lowered the standards and the media contain more defects. If a real-time CD burner hits a bad CD it stops, and you've lost the recording you were trying to make.
My solution is to back up all my recording. Everything sent to the CD burner for recording is also automatically sent to a solid-state recorder (a Marantz PMD 570) where it is recorded onto a reusable flash memory card. If anything goes wrong with the CD burn, I've still got a copy of the recording that I can bring into my computer and burn from there.
Backups are a good thing in other areas of life as well. It's good to have a backup business plan, a backup workout routine (for when the usual one hurts too much), backup clothing (for when you spill coffee all over your best suit), etc. It seems to me that a little paranoia can be a helpful thing.