The best you can do is use social media for registration. One of my boards uses 'Facebook' only registration, it is the type of board that people do not mind this kind of registration style. This will not work for the average board, but maybe yours fits the category. You should also know that the Facebook login in vbulletin will no longer function after December 21, 2014, unless it is updated to the new API.
Of course you cannot beat a "sexy awesome dork --- @disco_stu" if he signs up at Facebook as an alternate gender.