Bear with me on some maths here.
   Facebook says it will delete a milliard ‘faceprints’. In The Guardian: ‘Facebook will delete the “faceprints” of more than a[n American] billion people after announcing that it is shutting down its facial recognition system due to the “many concerns” about using the technology.’
   We know that you can turn on (and off) facial recognition in Facebook, to enable tagging. This came pretty suddenly, if I recall correctly. I turned it off immediately.
   The fact it came suddenly suggests that Facebook had already compiled these faceprints, because we all had the feature if we wanted to keep it. They must have been working on it behind the scenes for a while, before introducing it to every user.
   Now Facebook says it holds over an American billion, i.e. a milliard, of them.
   If we all had them, as we could turn them on and off at will, then it follows that Facebook only has just over a milliard users.
   This gels with their own research into new accounts, where they found that up to 56 per cent of them were owned by existing users. I’ve taken the higher figure here but, frankly, I think they’re underestimating.
   Now, Facebook claims it has 2·9 milliard users. Once again, just ask yourself: know anyone who’s recently joined? Exactly. Most of us don’t. So the user base shouldn’t be rising at the rate they claim. (We all know there are tons of bots on there.)
   On the assumption (you may think it’s a wild one) that their research is representative across all of Facebook, that 44 per cent of all accounts are legitimate and the remainder are owned by the 44 per cent, then:
 
2,900,000,000 × 0·44 = 1,276,000,000
 
   Remember not long ago I posited that Facebook’s actual user numbers were closer to a milliard?
   I don’t believe I’m far off, and this latest news might, if the logic holds up, suggest I’m right.
 
PS.: Thanks to Ton Zylstra for inspiring more maths on this. If Facebook finished 2020 on just under 2,000 million users, and now claims 2,900 million, yet the number of social media users increased last year by 400 million, you can pretty easily see their numbers do not add up.