This ideal of anonymity still persists in some Internet communities. But in many ways, the online world has turned out to be less private than the realm of flesh and blood. In part, that’s because most Internet users don’t want to cloak themselves in pseudonyms. Instead, they communicate in online spaces roughly the way they would in a room full of their closest friends, and use texts and e-mails the way they would once have used a letter or a phone call. Which means, inevitably, that they are much more exposed — to strangers and enemies, ex-lovers and ex-friends — than they would have been before their social lives migrated online. 

It is at least possible to participate in online culture while limiting this horizontal, peer-to-peer exposure. But it is practically impossible to protect your privacy vertically — from the service providers and social media networks and now security agencies that have access to your every click and text and e-mail. Even the powerful can’t cover their tracks, as David Petraeus discovered. In the surveillance state, everybody knows you’re a dog. 

And every looming technological breakthrough, from Google Glass to driverless cars, promises to make our every move and download a little easier to track. Already, Silicon Valley big shots tend to talk about privacy in roughly the same paternalist language favored by government spokesmen. “If you have something that you don’t want anyone to know,” Google’s Eric Schmidt told an interviewer in 2009, “maybe you shouldn’t be doing it in the first place.” 

The problem is that we have only one major point of reference when we debate what these trends might mean: the 20th-century totalitarian police state, whose every intrusion on privacy was in the service of tyrannical one-party rule. That model is useful for teasing out how authoritarian regimes will try to harness the Internet’s surveillance capabilities, but America isn’t about to turn into East Germany with Facebook pages. 

For us, the age of surveillance is more likely to drift toward what Alexis de Tocqueville described as “soft despotism” or what the Forbes columnist James Poulos has dubbed “the pink police state.” Our government will enjoy extraordinary, potentially tyrannical powers, but most citizens will be monitored without feeling persecuted or coerced. 

So instead of a climate of pervasive fear, there will be a chilling effect at the margins of political discourse, mostly affecting groups and opinions considered disreputable already. Instead of a top-down program of political repression, there will be a more haphazard pattern of politically motivated, Big Data-enabled abuses. (Think of the recent I.R.S. scandals, but with damaging personal information being leaked instead of donor lists.) 

In this atmosphere, radicalism and protest will seem riskier, paranoia will be more reasonable, and conspiracy theories will proliferate. But because genuinely dangerous people will often be pre-empted or more swiftly caught, the privacy-for-security swap will seem like a reasonable trade-off to many Americans — especially when there is no obvious alternative short of disconnecting from the Internet entirely. 

Welcome to the future. Just make sure you don’t have anything to hide.

One obvious example is the 2010 imbroglio involving a Harvard Law Student who had put her (reasonably well-informed and carefully nuanced) thoughts on the race and IQ question into a private email to two friends. A long time later, one of those ex-friends became a rival for a young man's affections, so the young woman's email was dredged up and leaked to a black organization, which set off a national frenzy. The dean of Harvard Law School, Martha Minow, condemned not the leaking of the private email but the author of the email.