Looking at the original Bitcoin client API I noticed one thing: once a wallet is encrypted with encryptwallet, there does not seem to be an API call that unencrypts the wallet.  Sure, you can change the passphrase with walletpassphrasechange, but the encryption remains.  Am I missing something, or is encryptwallet really a one-way street as far as the API is concerned?  (One could of course restore an unencrypted wallet from a backup, but that's not in discussion here).