I do look forward to our cyberpunk future where to "opt out" of certain systems, you have to paint a certain mark on your face, or put a little QRCode sticker on your cheek.

"Sorry, I'm only opted into Google Facemind and FacebookFace; I don't want to be indexed by Amazon Visage."

People have begun studying makeup and hair styles that foil today's face recognition in general: https://cvdazzle.com/

Or wear a government issue spook "ugly t-shirt".

Could be local only. New faces are saved as they're detected. Then later on your computer, add notes to the new faces ("John Smith, met 11/7/19 at Liz's party, programmer at Initech").

When those faces are re-detected, show the info text.

Would certainly be nice if you could do a similar thing without needing a camera on the glasses at all though. How can we recognize a person reliably without seeing them? Maybe by their voice?

I agree. Of course such system have some pretty important downsides. I'll perhaps have to pay more attention to people then.