Facebook made a startling admission in its earnings announcement this month: it was seeing a "decrease in daily users, specifically among teens". In other words, teenagers are still on Facebook; they're just not using it as much as they did. It was a landmark statement, since teens are the demographic who often point the rest of us towards the next big thing.
Their gradual exodus to messaging apps such as WhatsApp, WeChat and KakaoTalk boils down to Facebook becoming a victim of its own success. The road to gaining nearly 1.2 billion monthly active users has seen the mums, dads, aunts and uncles of the generation who pioneered Facebook join it too, spamming their walls with inspirational quotes and images of cute animals, and (shock, horror) commenting on their kids' photos. No surprise, then, that Facebook is no longer a place for uninhibited status updates about pub antics, but an obligatory communication tool that younger people maintain because everyone else does.
All the fun stuff is happening elsewhere. On their mobiles.