It took an impressively short four days for local and federal law enforcement to identify and hunt down Dzhokhar and Tamerlan Tzarnaev, the brothers accused of planting the bombs that killed three and wounded nearly 200 near the finish line of the Boston Marathon. Civil libertarians may be uncomfortable with this, but the authorities accomplished this feat of investigation largely through the magic of surveillance cameras.

The FBI and other law enforcement officials identified the two suspects by poring through gigabytes of images from the closed-circuit TV cameras in the area before and after the twin explosions — both those set up by the city of Boston and private cameras — and photos and videos sent in from spectators and marathon runners with smartphones and cameras. And the final manhunt started when surveillance cameras caught Dzhokhar Tzarnaev at a Cambridge 7-Eleven.

The FBI wasn't the only group trying to identify the perpetrators. The sometimes-sketchy web vigilantes at 4chan and contributors to Reddit launched efforts of their own, in one case scaring up a new, clear photo of Dzhokhar leaving the scene. The Tzarnaev brothers "shouldn't be surprised that surveillance cameras turned out to be their undoing," says Farhad Manjoo at Slate. "And neither should you."

Cameras are everywhere in America. New York City, for example, installed a "Ring of Steel" CCTV system — thousands of cameras to watch the public spaces of Manhattan — after the Sept. 11, 2001, attacks. And millions of smartphone-wielding Americans carry high-quality cameras in their pockets and purses everywhere they go. If even more accessible personal recording devices like Google Glass take off, you wouldn't be paranoid thinking that someone is watching you whenever you step out of the house.

That's kind of creepy. It smacks of Big Brother. But nobody not named Tzarnaev is disappointed that the murderers who targeted families and athletes in Boston on Monday have apparently been fingered so quickly. Of course, there's the downside of what we'll call false positives. The New York Post, for example, posted photos of two students on its cover Thursday, falsely suggesting they had something to do with the bombing. And in London, with its own half-million-camera-strong Ring of Steel, police shot an innocent man while trying to track down would-be bombers in 2005, notes Slate's Manjoo.

But all the very valid civil-libertarian concerns can be tackled with rules and regulations, says Manjoo. We should look at the Boston case as "a sign of the virtues of video surveillance," and we should push for even more cameras to monitor our public spaces.

Yes, you don't like to be watched. Neither do I. But of all the measures we might consider to improve security in an age of terrorism, installing surveillance cameras everywhere may be the best choice. They're cheap, less intrusive than many physical security systems, and — as will hopefully be the case with the Boston bombing — they can be extremely effective at solving crimes....

The best reason to welcome a government network of surveillance cameras is that we're already being watched — just not systematically, in a way that aids law enforcement. Private security cameras dot every busy street, and people's personal cameras are everywhere. It might have been valuable, at some point, for us to have a discussion about whether we wanted to go down the road of having cameras everywhere. But we missed that moment — instead, you and I and everyone we know went out and bought smartphones and began snapping photos incessantly. Nowadays, when anything big goes down, we all willingly cede our right to privacy — we all take it for granted that photos provide valuable insight into news events, and we flood the Web with pictures and clips of the scene of big news. [Slate]