This will trash tons of bitcoins because of users forgetting their passwords.
Maybe each bitcoin client could have a unique code built in to decrypt with by default so that the wallet.dat stays encrypted on the hard drive but users wouldn't need to remember their password if they use their same client.
How do you keep this unique code from the hackers? If they can access your wallet.dat, they can get at this code too.
Well, I was thinking of mechanism that uses the so-called "Trusted Computing Module" in your motherboard, or uses a secure key generated by your CPU's unique private key.