Backing up your data is an extremely important part of using your computer. With the threat of computer viruses, spyware, and other things that can go wrong with your computer it is a very devastating event when your computer crashes and you lose all your data. This is remedied by having a current backup of your data. You can be sure that your precious pictures or that important report for work or school is safe if you use a backup system.
I personally use Mozy. Mozy is a piece of software that backups your data in the background without you having to think about it. You get 2GB for free and the prices start at $3.95/mo + $0.50/GB so it scales with how much data you actually use.