The problem is that you must secure your wallet from both loss AND theft, but to reduce the chances of loss by making more backups, you increase your chances of theft.

The answer: use Shamir's secret-sharing scheme.

Wikipedia: http://en.wikipedia.org/wiki/Shamir's_Secret_Sharing
Command-line implementation (ssss): http://point-at-infinity.org/ssss/

You could store one copy on your hard drive, one you email to yourself, one on a USB key drive, one in a safe deposit box, one in your safe, one with a friend, etc.  If you have shares stored in 6 different locations, and you require 3 to recover the password to your encrypted wallet, then you can lose 3 of those shares with no problem!  A thief would also need to get 3 of the shares to recover the password.