I know you can't change your username, but can you change the password? I looked around but couldn't find a button or any such thing. If there is no provision for that, there ought to be. It would come in handy for account-sitting or if someone finds it out who you don't want to know.
The right answer to the wrong question is still the wrong answer to the real question.
Control Panel (left side) -> Profile (tab at the top of the user account panel) -> Edit account settings (link at the right side of the user account panel)
Kinda hard to find if you have no idea where to look, but the option exists.