This is not a niche phenomenon. Snapchat has more than 100 million monthly users. Line boasts that more than half a billion people message their friends through its service. Pinterest has about 60 million monthly users. Vine has more than 40 million registered users. The list goes on and on.

Social networking is not, it turns out, winner take all. In the past, one might have imagined that switching between Facebook and “some other network” would be difficult, but the smartphone interface makes it easy to be on a dozen networks. All messages come to the same place—the phone’s notifications screen—so what matters is what your friends are doing, not which apps they’re using.

Take a look at the rise of apps that exploit the desire for anonymity, ephemerality, and the unknown—roughly the opposite of Facebook’s founding desire to connect real people (under their real names) on the Internet.

Or take Yik Yak, the most radical of them all. If you’re over the age of 22, you’ve probably never heard of the app, whose sole purpose is to act as a virtual bulletin board for local spaces. People post on anonymous timelines visible to others who are physically close by. The UC Berkeley students who are sitting near me as I write this evidently like posting about classes, drinking, and sex, but mostly they just crack jokes. It’s a zero-commitment app for bullshitting and—maybe—connecting with someone in the physical world. And it regularly ranks among the top free apps for iPhones—below Facebook Messenger but sometimes above even better-known apps like Snapchat and Instagram.Snapchat, which allows its users to send each other self-destructing messages, has grown because people like snapping pictures that won’t go on their permanent record. Anonymous apps like Secret and Whisper allow people to shout things into the ether without worrying that someone will look in on that activity and socially punish them.

Right now, many mobile services merely replicate what people do on their computers. Yik Yak’s entire mechanism depends on where you are. It assumes that you already have ways to contact an extant social network—it takes Facebook for granted, even as it tries to undermine it. And if I were to put money on an area in which Facebook might be unable to dominate in the future, it would be apps that take advantage of physical proximity. Something radically new could arise on that front, whether it’s an evolution of Yik Yak or some service with an even dumber name.

A more direct challenge could come from a change in the media that people use to “talk” with one another. Judith Donath, who founded MIT’s Sociable Media Group and wrote The Social Machine, predicts that text will be a less and less important part of our asynchronous communications mix. Instead, she foresees a “very fluid interface” that would mix text with voice, video, sensor outputs (location, say, or vital signs), and who knows what else. Such an interface could be built by Facebook, but there’s no reason to think it has to be. Indeed, the forthcoming Apple Watch seems like a step toward the future Donath envisions. Users will be able to send animated smiley faces, drawings, voice snippets, and even their live heartbeats, which will be tapped out on the receiver’s wrist.