He discusses this very topic in Hypercritical, the podcast: [1], [2].

[1]: http://5by5.tv/hypercritical/2 [2]: http://5by5.tv/hypercritical/3

No he's overly paranoid when it comes to backups (if you listen to the ATP podcast this is very aparant) but in this case it's probably justified since there are many things that can go wrong with backups.