If I use GPG for my e-mails in Evolution, for every encrypted e-mail it asks for the password.
Why not implement this also in a bitcoin client: for every transaction the password is required, and the wallet is decrypted but not saved on HD, only in RAM when it is needed for the transaction.
This way the wallet is never decrypted in a file on the HD and is difficult to be stolen.
The GPG keys are replaced periodically. If you forget the passphrase, you are not likely to lose large sums of money. A savings wallet may be stored for decades. Are you really going to remember a passphrase consisting of 32 random digits in 10 years?
Computers are now fast enough that you pretty much have to write down important secure passwords (With the security implications understood my most).
Take-away: good passphrases are hard.