You know you should be! If you're not, go check out my newest article for Computing Unplugged at http://www.computingunplugged.com/issues/issue200906/00002389001.html for eight easy-to-follow steps to make sure you back up everything you'll ever need.
So important, especially for anyone who uses their computer to invent/write/create things. Lesson plans, knit or crochet patterns, books... do you really want to re-invent them after a crash? I doubt it. :)