3 billion monthly active users. They hit 2 billion this summer [1].
[1] https://www.theverge.com/2017/6/27/15880494/facebook-2-billi...
[1] https://www.theverge.com/2017/6/27/15880494/facebook-2-billi...
I was trying to suggest that a lot of those "users" are not sources of income/data. I'll bet a lot of them are either bots, or humans smart enough to use an ad blocker. And most of the MAU humans are probably in a 10-year age range, having signed up when FB was useful.