Facebook and Facial Recognition Technology
"We are able to suggest that your friend tag you in a picture by scanning and comparing your friend’s pictures to information we’ve put together from your profile pictures and the other photos in which you’ve been tagged. If this feature is enabled for you, you can control whether we suggest that another user tag you in a photo using the “Timeline and Tagging” settings. Learn more at https://www.facebook.com/help/tag-suggestions.
We currently use facial recognition software that uses an algorithm to calculate a unique number (“template”) based on someone’s facial features, like the distance between the eyes, nose and ears. This template is based on your profile pictures and photos you’ve been tagged in on Facebook. We use these templates to help you tag photos by suggesting tags of your friends. If you un-tag yourself from a photo, that photo is not used to create the template. We also couldn’t use a template to recreate an image of you.”