Above: Wojciech Braszczok, the undercover NYPD biker cop who took part in the assault on an SUV driver and worked undercover in Occupy Wall Street.

The city now has a sturdy legion of undercover officers who have taken up residence in many surprising regions of civic life. Much of this began in early 2003, when a federal judge lifted many restraints on spying by the Police Department. The city had been failed by the federal intelligence services, and thousands died on Sept. 11. Police Commissioner Raymond W. Kelly and Mayor Michael R. Bloomberg created an independent intelligence capacity.

So before and during the Iraq War, the organization of antiwar rallies was regarded as a fit matter for police surveillance; so were the monthly Critical Mass bicycle rallies, as well as groups protesting at the Republican National Convention in 2004, and a range of Islamic facilities, from mosques to college student clubs. Undercover New York police officers showed up at activists’ meetings all over the country, carrying guitars and knapsacks. Handlers left money for them in the wheel wells of cars. Field reports were stamped “NYPD Secret.” Anyone who left a scrap of paper on the desk at the Intelligence Division’s headquarters in Chelsea was apt to get his or her knuckles rapped by the commander, a former Central Intelligence Agency man who brought that agency’s custom of fastidiousness to the mess of the city.

The unrestrained surveillance in New York public life is the physical embodiment of what has been taking place online over the last decade under operations of the National Security Agency revealed by Edward J. Snowden. To borrow the title of a 1918 novel about nosy Irish villagers, we have become The Valley of the Squinting Windows.

But it was all O.K. because the mayor and the police commissioner said so, though from the outside, no one could really say what they were up to.

Detective Braszczok was arrested this week and charged with being part of a gang of motorcycle riders who turned a traffic dispute into a smallish riot directed against a man at the wheel of a sport utility vehicle with his family inside. The detective’s credential as an undercover officer jolted many people into paying attention. “We sent out his pictures to everyone on our list this morning, and asked if anyone knew him,” said Bill DiPaola, a leader of Time’s Up, an organization that advocates for improved circumstances for bicycles.

Soon, the detective’s participation in Occupy Wall Street was documented with pictures. No doubt video will surface soon: every one of us is now a videographer in an age of free-range history. Gothamist reported that he posted on Twitter as @evovillen about the Occupy Sandy operation:

“*SANDY SPECIAL PART 3* REBUILDING OCCUPY TO CONNECT, MOBILIZE AND CO-CREATE WITH, assembly Happening at 60 wall today.”

Gothamist’s Web site quoted a member of the Sandy relief operation saying that the detective was a regular at the two main distribution depots set up by the group in Brooklyn. He attended an activist’s birthday party at the Blarney stone in Lower Manhattan.

One of the large, undiscussed questions of such surveillance is how civic dialogue can be influenced or distorted by police agents — perhaps as provocateurs, or possibly with no motive beyond maintaining cover. During the Republican convention, after a group making a film was arrested, a redheaded man standing on the street pounded on the back window of a police van, urging that the people inside be let go. A day later, the same man was videotaped being briefly put under a fake arrest, leading to tumult in the street from others who objected to his incarceration. They were unaware that the man was an undercover police officer who was walked down the street by uniformed officers, hands behind his back but uncuffed, and sent on his way: catch and release.

The city has maintained that the expanded surveillance is necessary to keep society safe. No one in the Bloomberg administration has discussed the limits on their participation in public dialogue. Or, for that matter, why they ought to be standing alongside people handing out bags of groceries.