I've lost track of the number of people who've asked me to comment on David Cameron's insane plan to cripple Britain's internet in times of civil unrest by blocking Twitter and other services. In case you're wondering where I come down on it, well, let's say that it's not just a bad plan, it's also an ineffective one.

It's only been a week, after all, since Cameron's government concluded that the Digital Economy Act's web censorship plan wouldn't be implemented because downloaders would have no trouble getting around the blocks it would throw up. If people who want to download movies can evade Britain's censorwall, then so can people who want to organise riots. Duh.

But for me, the use of BlackBerrys in organising riots (if "organise" is the correct verb here) is just a sideshow. Though as a Canadian, I'm fascinated to see that our national technology success story, the businesslike BlackBerry, has now enduringly entered pop culture's lexicon as the tool of choice for disaffected and violent youth.

The real story for me is about surveillance, and not the mere use of CCTV footage to apprehend rioters after the fact. It's about the total failure of CCTV to deter people from committing crimes in the first place.

After all, that's how we were sold on CCTV – not mere forensics after the fact, but deterrence. And although study after study has concluded that CCTVs don't deter most crime (a famous San Francisco study showed that, at best, street crime shifted a few metres down the pavement when the CCTV went up), we've been told for years that we must all submit to being photographed all the time because it would keep the people around us from beating us, robbing us, burning our buildings and burglarising our homes.

A year before the Vancouver Winter Olympics, a reporter from a one of the local papers called me to ask whether I thought an aggressive plan to use CCTVs in the Gastown neighbourhood would help pacify the notorious high-crime heroin district. I said that the deterrence theory of CCTV relied on the idea that the deterred were making smart choices about their futures and would avoid crime if the consequences might catch up with them.

Then I recounted my last trip through Gastown, where the pavements were thronged with groaning and unconscious emaciated addicts, filthy and covered in weeping sores, and asked if those people could be reasonably characterised as "making smart choices about their future." I explained how my hire car had been broken into by a thief who'd left four perfect fingerprints on the passenger window, not caring whether the crime was associated with her or his biometrics forever.

Funnily enough, I was in Vancouver during the riots, which took place quite close to my home in London. I went through Gastown, which is utterly transformed into a pleasant shopping and university district. Simon Fraser University very carefully and cleverly slotted a new campus into the middle of Gastown, and hired only local people to work in it.

It was the very model of giving people a chance and a stake in their neighbourhood. And while there are still some sad and disfigured junkies here and there, you'd never know that Gastown was recently notorious as the most drug-blighted neighbourhood in the city that is the major port of ingress for heroin into the Americas.

I won't pretend to understand the forces that led my neighbours to take to the street and smash and burn and hurt each other. I don't think I know what "pure and simple criminality" is – presumably, it's some imperceptible pollen that drifts through society and alights on people, which is awfully convenient for government because "pure and simple" criminality has no cause and therefore no one to blame and nothing that can be done to prevent it.

But I do understand one thing: the deterrence theory of surveillance had no nexus with the motivations of the rioters. The theory of street crime as a rational act is bankrupt. Evidence-led CCTV deployment shows us where CCTV does work, and that's in situations where crimes are planned, not pulled off in the heat of the moment.

Parking garages, banks and jewelry stores, yes. And CCTVs make perfect sense as part of burglar alarms that switch on when the glass breaks (or buffer continuously, but only save the few seconds before a break-in). But the idea that we can all be made to behave if only we are watched closely enough all the time is bunkum. We behave ourselves because of our social contract, the collection of written and unwritten rules that bind us together by instilling us with internal surveillance in the form of conscience and aspiration. CCTVs everywhere are an invitation to walk away from the contract and our duty to one another, to become the lawlessness the CCTV is meant to prevent.

After the London riots, one thing is certain: anyone promoting CCTVs for deterrence is most likely selling something, probably CCTVs.