If you don't backup your writing then for crying out loud what the heck are you playing at? Having recently switched computers, I've been taking the opportunity to improve my own backup system. Apart from all our photos, music and videos, I have my entire novel in various states and formats on my computer. In fact, my hard drive contains pretty much everything I've ever written, fiction or otherwise.
Anyway, the one thing I've never had is off-site backup, which is pretty silly of me. This post from everyone's favourite internet chieftain, Shawn Blanc, gives you a detailed overview of the various options out there. He also spells out why off-site backup is so important:
What if our home was destroyed and we lost all our belongings? Or what if someone were to break in and rob us? Apart from one another, the only irreplaceable things in our house are the priceless memories, work, and other information that we keep on our computers.
I know what it's like to work on a piece of writing, say a few hundred words, and accidentally close down without saving. I daresay you do too. Imagine that feeling on a much grander scale. Gracious. It's gives me the willies just thinking about it.
Read Shawn's article. Backup your work.