Mr. May:
One of the interesting things is that _ear shape_ is one of the best correlation features.
Of course, to measure ear shape the camera has to have a good view, unobscured and at close enough range to get a decent number of pixels. (This makes sense, that ear shape would be a good metric. I've been noticing the variations in ear shapes since I heard about this scheme. Also, I can imagine the various conformal transformations--different angles of view, for example--preserve certain relationships well.)
Hmmm... Maybe it's time to market a line of Privacy Ear Jewelry. Shouldn't be hard with a couple piercing here, and some funny lumps there to distort the profile enough. -- http://www.apa.org/journals/psp/psp7761121.html It is one of the essential features of such incompetence that the person so afflicted is incapable of knowing that he is incompetent. To have such knowledge would already be to remedy a good portion of the offense.