It is difficult to pinpoint the precise moment that the privacy norm died, but historians tend to emphasize a few key developments. The global adoption of the Internet, World Wide Web, and smartphones were obviously the beginning. The rise of services that gathered user data to monetize through various strategies on the one hand, and systemic state surveillance such as was practiced early on in China on the other. A few open source projects which made it trivially easy for even the technologically unsavvy to get around all but the strictest security practices.
Whatever moment in these and other progressions it happened, the notion of “secret” gradually expired while no one was looking. The result was a radically transparent society unprecedented in human history.
The initial discontinuity clearly occurred a few short decades after the birth of the Web, and the result was a great deal of disruption and upheaval at first. It took less than a generation, however, for people to simply become used to it.
Philosophers and scholars before the great transformation believed that people would behave fundamentally differently when they were being observed, but it turned out that people can get used to just about anything. And when they do, they tend to just keep on falling into the same old patterns. So while a sociologist of the late 20th century might have thought that porn consumption—especially of the really weird stuff—would plummet if anyone anywhere could find out about it, it remained basically unchanged. For the most part, people didn’t want to know what porn other people were watching, and taboos developed against bringing it up even when they did find out and were disgusted by what they learned.
There was a lot of fear about what what happen under a mass surveillance state. But the private lives of the state officials who would pursue prosecution were also an open book, and any unsavory personal or organizational agendas were in plain view. As a result, in those countries where success in the public sector was highly sensitive to public perceptions, the transition was basically a wash. In police states such as China, tyrannical laws were already selectively enforced to begin with. The new transparency made it clear how large a swath of the population was dissatisfied, and how corrupt the ruling regime was. It also made it harder to stop insurgents from finding and doing harm to top officials, though it made it easier to find them after the fact.
In short, the result of an initial upsurge in violence and persecution was largely a shift in norms that kept social and political life in the status quo.
A few generations in, when history teachers explained to their students that their ancestors had clung fiercely to concepts of privacy and secrecy, they were baffled. How did any solve any crimes? What did the older generations think they had to hide? Of course, as with the young of any era, it was inconceivable to them that society could ever have functioned at all outside of the particular framework they grew up in. Even though they continued to be taught that crime rates and wars and censorship around the world had basically remained the same before and after the transition, few could bring themselves to believe it.
The preferred the story of progress, the story of how technology transformed the world for the better.
Stories about how the world keeps on turning, mostly indifferent to the things individuals find fascinating, are boring, and soon forgotten.