> Sounds like always wearing sunglasses when in public should be a basic measure of getting privacy from the government

I've heard about that solution, but I wonder if it really works. For example, using just the shape of your sunglasses and the shape of your chin, probably you could be uniquely tracked if not identified. To identify you, other physical features may work (nose, chin, gait, etc.).

Biometric ear recognition. Google it, there's plenty of research in this area.

See also: CV Dazzle, a fashion trend designed to foil face detectors like Viola Jones (which is pretty easy to foil) or face recognition algorithms (which are all horrible wrt occlusion these days): http://cvdazzle.com/

Supposedly some facial recognition systems are designed with things like that in mind. They are meant to be invariant to hair style, sun glasses, facial hair, etc. If they weren't they would be less useful.

What about then "they" aren't even human!? /s