Laurie Penny: In the age of camera phones the message is that protesters are watching police too

Eyewitness: There are droves of old-school peace activists and war veterans, but many of the younger attendees have a broader economic agenda

As a thousand protesters carrying anarchist flags and wearing gas masks march up State Street in Chicago, you can't see the cops for the cameras. Hundreds of police officers form walls of flesh, steel and plastic to divide protesters from the Nato delegates sleeping in hotels yards away, and find themselves confronted by a forest of camera-phones and video equipment whenever they attempt to make an arrest. It's hard to tell those taking pictures for the press from those who are simply holding up their cameras because it makes them feel powerful.

Faced with multimillion-dollar policing and surveillance operations that burden even the most peaceful protest with the threat of felony charges, while Wall Street workers guilty of colossal financial fraud continue to go unpunished, holding up a camera is about the only thing that does make ordinary Americans feel powerful.

Americans of all ages, races and political affiliations have travelled from across the nation to take a stand against this week's Nato summit, from disgruntled mid-western Democrats to Clownbloq, a phalanx of "anarchist clowns".

There are droves of old-school peace activists and war veterans, but many of the younger attendees have a broader economic agenda. "I'm definitely not someone who's totally against all military intervention by the US, and I don't necessarily think everything the US does is evil," says Gabriel, 19, an Occupy Wall Street activist who travelled from New York. "I just think we need to be spending a lot less money on things like Nato and more money on education, healthcare and transportation."

By the eve of the summit, 45 people had already been arrested, according to the National Lawyers' Guild. These included three young men seized in a raid on a house where they were allegedly making Molotov cocktails. The so-called "Nato Three" have been charged with conspiracy to commit terrorism, although their defence lawyers are already alleging entrapment.

In the early hours of Sunday two prominent "live-streamers" – radical camera operators who broadcast a continuous feed of protest and police activity – were cuffed and interrogated at gunpoint by Chicago police. Tim Pool and Luke Rudowski, both in their mid-twenties, are probably the people least likely to be doing anything illegal at any demonstration, given that they have multiple live cameras strapped to their chests.

That they were apparently targeted for intimidation suggests the authorities are still unable to handle this new kind of people power – the notion that in an age of state surveillance, ordinary people can watch the watchers right back.