The Russians have already done this: https://www.google.com/amp/s/amp.theguardian.com/technology/...

Discreetly snap someone's photo and there's an excellent chance that face recognition will fond their social media profile. Now you have their name and potentially a lot more (age, school, hometown, etc).

All it takes is enough centralization and a culture of sharing a lot online and you're loving in the future!