Facial recognition: - Need unobscured face (crowds). - Complicated by changes in features and environment. - Unique IDs are something you ascribe to faces, n

Facial recognition: - Need unobscured face (crowds). - Complicated by changes in features and environment. - Unique IDs are something you ascribe to faces, not something they hand to you on a plate. - Sophisticated analysis needed. Example: even Baidu uses custom tricks for their facial recognition office ID with a known database of mugshots. I.e. not an unknown number of people in various conditions. RFID: - AFAIK can read many tags at once. - No need for line of sight. - Tags hand over a (likely) unique ID on demand - No need for deep learning experts at $100k> Seems to me microchips would be far easier to achieve creepy levels of tracking with.