You peeps sound paranoid to me. When you xerox a document do you usually also make 2 copies and store one in a different location "just in case"?
Actually, in my experience, hdd or cd/dvd back up is extremely reliable, safe and rarely will anything go wrong. Unless you do stupid things like using a CD with one years worth back up as a coaster for a coffee mug. Believe me, peeps do that --I saw one peep at my office using his laptop's restore CD, face down so if it scratches it makes it useless, as a coaster for a paper weight. Dude jsut didn't care or get it.
But, yeah, one back up is essential.