A hoax hit Facebook this week. Fake news about a fake app called Facezam claimed that the app could track down anyone by simply scanning their Facebook photos.Thousands or millions of Facebook users fell for the hoax and freaked out. (A U.K. marketing agency created the hoax as a publicity stunt.)The public reaction illustrates how confused people are about face recognition. In fact, everything the fake Facezam was said to do is easily done with real apps and sites.The public is understandably hazy about the privacy and security risks of biometrics. Everybody knows biological features can be used to identify people. Police have been using fingerprints for decades, for example.Technology has enabled a large number of new biometric identification systems that use fingerprints, iris scans, wrist vein scans, voice recognition and face recognition. But when it comes to the potential for privacy invasion, however, these various approaches are not equal.