No seriously who is she?  Your guess is as good as mine, but what I can piece together from some reputable news sources is that it's Beyonce's new alter ego.  Anyway if you think you know who Sasha Fierce is call 917-388-9229 now and give the people your answer to get opted-in to the Sasha Fierce Mobile Mob.  One lucky person with the correct answer will be randomly chosen to receive a personal message from Sasha Fierce when she is ready to unveil her identity.  And, please let me know what all of this means when you find out.