[jaclaz]

Yep, but as said above that would be "big data" with the need of de-duplicating them and with no additional (reliable) parameters.

Then you will need some AI (or whatever) to remove non-human photos or non-suitable photos (position, lighting, etc.) whilst this method would almost guarantee only "portraits" or "upper torso" pictures of humans.

What I tried to say wasn't that this is the "only" method, but that it is one of the "easy" ones with a high probability of getting "reliable" data.