I am not sure if the rules have changed but they told I would not get miles both an individual and a joint account with my wife but they did give me the 5K bonus for referring her (the referree must respond to an e-mail with a message from the referrer for you to get the bonus) and we opened separate accounts and both got the regular bonus.
One word of warning be very careful with e-trade had a lot of problems with them and closed my account before the required 6 months, they did not take their miles back (so far anyway).
Mike