Just thinking aloud here, but if your user name is the email address, you could actually store a hash of the user name, use that to look up the account and veri

Just thinking aloud here, but if your user name is the email address, you could actually store a hash of the user name, use that to look up the account and verify the login, then keep a map from the hash to the user-entered name in an in-memory database. This way the user name (email address) never gets stored. This would also work when someone has forgotten their password, as long as they don't forget the email address they used to sign up. (This is actually the only reason why the user name has to be the same as the email address.) You can't send regular information emails with this, though.