Have you ever seen a situation in which the source and the backup both fail simultaneously? (*edit - two hard drives on a single striped raid would still be one source).

The main storage of my images is on my primary desktop, which is backed up periodically to an external ESata drive, which is otherwise left off and stationary. It would be one heck of a struck-by-lightning coincidence that they both fail me at the same time, I am more worried about winning powerball than I am both drives failing me simultaneously. Hence, why I call it asinine.