When you ask hypotheticals like this, it comes across as an attack. When you attack people, they stop showing up to share their unique knowledge and experience.
One question, do you construct "templates" for faces that are unmatched by existing templates that are correlated?
This would allow a shadow face recognition profile to be generated that could be later matched to a known image.
I've had face recognition turned off anyway, and I'm not particularly concerned about it, I'm interested though in how internally FB manages "unknown" images, shadow profiles etc.
When are you going to fix the 2FA account issue I noted last year? I'm beyond responsible disclosure times, y'all have been totally silent (which has had the consequence of me being unable to access my account for a year) and I think I'd like to be going public with it really soon.
The feature is now opt-in. It is turned off for all new users and for those who only had the "tag suggestion" setting on.
Disclaimer: I work at Facebook and this feature is managed by my team.