Given how cheap disk space is, there's no excuse for having at least some sort of backup system. I'm appalled by how many people I know who have no backups of any kind. I'm especially concerned for people who only have laptps.
What are you going to do if that laptop gets stolen or run over by a bus or has water dumped on it?
The main question you have to ask yourself is
If my computer completely failed right this second, what would I
You have some shopping to do if the answer to that question scares you.
Go buy a copy of  and a .
You can get almost total peace of mind for under $200.
That first step is the most important. But there's another thing to worry about
What happens if my house burns down and I lose my computer and my
Some people might be comfortable ignoring that level of paranoia. If you took the first step and are comfortable stopping there, go ahead and stop
I've been burned a couple of times before so I'm a little more paranoid. Here's my setup:
- A Linux fileserver which serves as a backup to my two Windows machines. The My Documents folders on my Windows machine also point to network shares on the fileserver
- One of the Windows machines has a second 500gb SATA drive in it that serves as a backup to a number of files from the Linux fileserver (like the My Documents folders)
All of the backups happen automatically via cronjobs twice a day. I have a few very simple Bash scripts that use rsync to do incremental backups. This system has served me well and I've had to go to those backups several times.
In the end, I settled on  which uses Amazon S3 for online storage.
I paid $20 for the full version of Jungle Disk (there's a free trial too) and I'll be paying $0.15/gb/month to actually store the data at Amazon S3 (you also pay $0.15/gb for transfers in and out).
It's nice too because I'm not locked into Jungle Disk (which is great so far). I can use an Amazon S3 compliant client to get files in and out.
I hear sob stories from people who've lost all of their digital pictures/mp3s/etc and I have very little sympathy because it's too easy to avoid.
So get out there and make sure your data is protected.
: http://www.acronis.com/homecomputing/products/trueimage/ : http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=2010150414%20131021357&name=400GB%20-%20750GB : http://www.jungledisk.com/