Does Mt. Gox's "Redeem a wallet.dat" feature require an unencrypted wallet? Just added to Mt. Gox's API documentation is the ability to Redeem a wallet.dat, which allows a simple way to import (via upload of wallet.dat) all your private keys to be managed by Mt. Gox.

All bitcoin amounts in your wallet will be transferred to your Mt. Gox account and any amounts received later will be swept at that time as well.

Does this feature work with an encryption-protected wallet.dat though?  The API doesn't show any way to send the passphrase as far as I can tell.
To do this Mt.Gox must have unencrypted wallet.dat.  Technically, you will have to either unencrypt yourself, or provide passphrase to Mt.Gox.  Which depend how Mt.Gox manage feature.  Maybe both work. 

Be very careful how transmit wallet and passphrase.  Use some good encryption, https if doing via web, PGP (encrypt mode, not sign mode) if doing via mail.  Transmit unencrypted wallet, or encrypted wallet with unencrypted passphrase, must have first secure channel.

Also must trust Mt.Gox.  Mt.Gox has US$5M seized from accounts in last few days, and now under investigation American gov't.  Maybe difficulty paying you, specially if paying US$.  Maybe motivated give up customer secrets.  Maybe American gov't right.  Something to think about. 

Cant say for you, but I would never use such service.  Suspicious bastard, me.