I'm sceptical of the monthly active users number as it also includes Facebook Messenger users that might not ever use the website or app itself.

From my social circle outside the tech world, Facebook is increasingly being frowned upon - and in the teens age bracket , Facebook is what old people (parents and so on) use. Obviously anecdata, but the general feeling is that people use it less and less. There might be a perfect storm coming for Facebook - or it's just a temporary fart, soon to be forgotten.