I was wondering the same thing. Re: if anything happened to me, I want my wife to be able to load my wallet on to her computer. She also has a wallet with some coins on her computer because I had her install the client and sent her some. So I was thinking on the client should be able to manage multiple wallets and have a procedure to import a wallet from something like a flash drive. It would give instructions on proper handling of the wallet on the original computer(u must delete it now and not try to use it).

When you say you can lose your bitcoins if used from two different computers, does that mean just running the client or actually sending the same bitcoin?

What happens if someone steals your computer with your wallet and you have a backup?
When you go to send all your backed up bitcoins to a new address before the thief can, what will happen?