Why is the automatic login disabled for users with encrypted home?

I've tried to setup an autologin, but that isn't possible, because my home is encrypted. What are the reasons for this?

PS. Here I have described my problem: Ubuntu Netbook Edition and automatic login.

Solution 1:

The problem is that your password is required to unwrap the mount passphrase used to decrypt the eCryptfs home directory. Without that, it's not possible; the system doesn't have the encryption key yet.

These login styles are mutually exclusive; you can either automatically log in (thereby letting anyone with physical access to your computer be able to access your data), or you can encrypt your home directory (keeping things encrypted and safe from access without a passphrase), but not both.