After following a liveblog of the presentation where Google announced Ice Cream Sandwich, one of the more interesting features announced was the ability to unlock your phone with your face. As in, the front facing camera is able to determine if the person in front of the camera is the owner of the phone.
What is the rate of false positives and false negatives for this feature? Can it be fooled by a photograph of the owner of the device? If it fails to unlock automatically, is there a fallback password/pin mechanism to unlock the device?