In the current system if a user is registered via social network is not allowed to associate a password to your user. In fact if he tries to recover his password, the email is sent, but then when he clicks on the link it does nothing.
We have detected several cases of users who, in addition to their social network login, would like to have the possibility of logging in using their username/password.
The opposite case is allowed, i.e. a user with a password, if he logs in through the social network and the email matches, the social network is linked and has two identities.