Same here, not only do I back them up on external HD, I also burn them to CD or DVD. I've also had an external HD crap out on me. I lost a lot of stuff off that drive and never recovered it.
Weekly automated backups to a RAID (they're cheap!) that you then validate occurred. As important as the stuff on our computers is to us can't believe people don't take precautions. I've had two hard drives die and with simple precautions I've lost nothing. It's not rocket science.