Harddrives fail, it is a fact of computing. When they die, it sucks. At the least, it will cost you some time when you replace the broken hardware. If you don't have copies of your data elsewhere, you will suffer the worst outcome, lost files.
If those files happen to be images, that could really suck!
There is a certain subset of my images that I would be devastated if they disappeared. My first serious digital camera was bought about 6 weeks before my son was born. Since that time all my family photos have been digital. They are irreplaceable. Tobias will never be 1 day old again, Kathryn will never again have a fifth birthday party. These are the pictures that compel me to have backups.
If you don't backup, START RIGHT NOW!!
Here is my current backup/storage strategy for those looking for ideas: I have a USB "cradle" that accepts SATA drives. I have two 500GB drives that I copy my files to using this cradle. One stays with me, and I take the other one elsewhere. These are my "cold" backups. I rotate them between home and offsite monthly. My "live" storage is a two-disk Buffalo RAID. It has a copy of all my digital pictures since 2006 on it. Finally, I have a RAID in my computer. I currently have all my files from 2008 forward on it. I consider this drive my "working" area.
I use a program called SyncBack to help manage the copies.
Anyone want to share their backup scheme?