Mark Zuckerberg believes that every year, people share twice as much online as they did the year before. It is perhaps less a prophecy than an ethos, or maybe more a kind of threat. After all, each new Facebook product is designed to get people to do exactly that: share more.

Facebook Home, for example, injects Facebook directly into the most personal computer you own, your phone. It takes over text messaging, and fresh Facebook content appears every time you turn on the device’s display. It is a constant reminder that you could—should!—be sharing whatever you’re doing with your Facebook friends, in part so that Facebook and its partners can use your detritus to develop a more complete profile of who you are.

That “share more” ethos has become canonical within technology companies outside of Facebook, as well—a free product necessitates advertising as a business model, which means they are selling you, and they need more of you to sell more things. Perhaps the most insidious push to share more is coming from services that broadcast your taste. “What really matters is what you like, not what you are like. Books, records, films—these things matter,” John Cusack’s character said in “High Fidelity.” This is true, in a way. There is perhaps no better sense of who you are in a given moment than what you are listening to or watching, and music-streaming services like Spotify and Rdio are designed by default to keep your friends informed about every single song you listen to, while Netflix, recently freed from its legislative bonds, now encourages you to broadcast what you are watching. Through these services, a ceaseless stream of the pop culture running through your brain is disseminated to your friends. Life becomes an unending performance, one captured and endlessly teased apart by data scientists and marketers.

At South by Southwest, I saw a device called Memoto, a discreet thirty-six by thirty-six millimetre wearable camera that automatically snaps a photo every thirty seconds, which will be released later this year for two hundred and eighty dollars. It’s designed to be a user’s personal “lifelog,” and it stops taking pictures only when it is placed in a pocket or face-down on a table. Otherwise, essentially every moment of a user’s life becomes shareable; he or she is never not performing for a potential audience. (As is anybody who comes across the camera’s path—another new norm, suggests the company’s founder, Martin Källström: “Norms have shifted to the point where, in most social settings, you can pick up your phone and take a photo without asking people around you if that’s O.K. That’s the same thing that allows us now to get a purely positive response from people.”)

Our behaviors change, as do the things we like, yet every aspect of a person that is shared through these services goes toward creating what is intended to be a durable record, one that is catalogued and indexed for later viewing on Facebook or Google or Twitter. And permanence, by its nature, offers a pretense of truth. This Spotify stream and those Facebook photos and the links they shared are who that person really is, right? Or at least close enough?

In that context, the rise of Snapchat among the under-twenty-five set, who have spent their formative years with Facebook looming in the background, is wholly unsurprising. Snapchat is a photo- and video-messaging service that deletes images and videos from a recipient’s phone within ten seconds; every shot is ephemeral. As of this past February, the service handled sixty million photos a day. When I spoke to the Snapchat founder Evan Spiegel a little while ago, he would not quite commit to the idea that Snapchat is potentially part of a bigger movement against permanence. “It’s hard for me to say,” he said, even as he noted that “our entire lives have been liked, retweeted, posted, forwarded” with a touch of lament. But he offered that Snapchat allows you to “free yourself from an amorphous collection of who you’ve been forever.”

Snapchat highlights the power of deletion in resisting the gentle totalitarianism of endless sharing. Deletion pokes holes in these records; it is a destabilizing force that calls into question their authority, particularly as complete documentation of a person’s online identity, which Facebook and Twitter increasingly purport to be. It is the only way to be selective, to make choices, when everything is shared. I delete tweets frequently from Twitter, for instance. (I have jokingly called it “snaptweeting.”) There is a general expectation that a tweet will stick around, particularly if it is somehow embedded in the greater Twitter infrastructure, for example when somebody favorites or retweets it. Its disappearance shortly thereafter breaks the system in a tiny way, generating a hairline crack in that model of who I am.

A social-networking executive I spoke to at SXSW remarked, in all seriousness, that the future of privacy is “lying.” But it’s quite difficult to lie all the time in the face of constant surveillance. If we can no longer keep anything to ourselves, deletion may be privacy. It is perhaps telling, though, that when I asked Memoto’s Källström about deleting photos from the lifelog, he said that the function had not yet been implemented into the software.

Illustration by Jordan Awan