Which brings us back to the question: Have we reached peak Facebook? And no, we haven’t. Even if Facebook never adds another user, it will keep growing: It has become a fundamental substrate, a difficult-to-avoid component of any site or app that requires users to register—making it essential to nearly every major web innovation now and in the future.

There’s a related question: Is Facebook ever going to be cool again? That’s like asking “Is the phone company cool?” The interface may not be exciting anymore, but the network is very, very cool, in the disruptively awesome way that enormous things are: volcanoes, aircraft carriers, the New Deal.

Tens of millions of people made a decision to spend their time with the simple, mobile photo-sharing application that was not Facebook because they liked its subtle interface and little filters. And so Facebook bought the thing that is hardest to fake. It bought sincerity.

Instagram succeeded for many good reasons, including its design, its viral qualities, its simplicity, and the fact that its engineers focused so obsessively on making sure that it works all the time. Part of its success, no doubt, is the fact that it was just in the right place, at the right time, with the right, crowd-pleasing mix of features.