social networks the tyrant's weapon of choice too...,

The Independent | We've seen the incredible potential for technology to empower citizens and the dignity of those who stand up for a better future," said President Obama on Tuesday night, after he had just come off the phone from speaking to Egypt's embattled leader, Hosni Mubarak. To which one can say: yes and no. For the sense in which Mr Obama is correct may be quite limited. Undoubtedly, it is much easier to organise a demonstration than it used to be. You can call people from your mobile phone, send text messages, use Facebook, dispatch a tweet to your friends or fire off email messages. We are all connected now.

But also note what the head of police in Iran, Esmaeil Ahmadi Moghaddam, is doing. A few days ago, he proudly announced the launch of cyber-police units throughout the country to confront internet crimes and to counter social networks that spread "espionage and riots". The police chief said the cyber-police would take on anti-revolutionary and dissident groups who used internet-based social networks in 2009 to trigger protests against the re-election of President Mahmoud Ahmadinejad. "Through these very social networks in our country, anti-revolutionary groups and dissidents found each other and contacted foreign countries and triggered riots." Iran is not going to put up with that, he was saying.

So the technology to which the US President was referring is available equally to friend and foe. Take the mobile phone, for instance. The Egyptian government had a crude answer to all this potential-for-technology-to-empower-citizens stuff. Once the demonstrations became serious, it swiftly closed down all mobile phone services. Only yesterday did mobile phone communications begin to come back. In fact, governments don't have to shut down the whole mobile network; they can content themselves with switching off a single city or even parts of it. And while News Of The World journalists have proved adept at hacking into voicemail messages, many authoritarian governments can do better than that. They can use technology that allows them to interrupt the delivery of text messages that contain what they consider to be suspicious words.

There is a further aspect of mobile phones of which organisers of demonstrations need to be aware. Your location can be established by joining up the "lines" between local base stations. This is not an obscure technique. As Evgeny Morozov points out in his important book, The Net Delusion: How Not To Liberate The World, published last month, mobile companies have strong economic incentives to improve their location-identification technology so that they can sell geographically targeted advertising. If businesses can use it, so can police forces. When you are standing in the middle of Cairo's Tahrir Square, squashed among thousands of demonstrators, with your mobile in your pocket, switched on, you are not necessarily as well hidden or anonymous as you might wish.

Mr Morozov gives a frightening analysis of how authoritarian governments can harness the new technologies of the internet age. Social networking sites, for instance, make it easy to find one's friends who are already members, but cyber-police can use the same facilities for their own purposes. Nor do authoritarian governments try to do everything themselves. They force the companies that run the internet to police the web according to broad guidelines. This is the way Chinese censorship is going. In its essence, it is not so very different from the way in which the US Government went about putting pressure on companies that extended financial services to Julian Assange's whistleblower website, WikiLeaks. From the point of view of the authorities, the nice thing about this is that the companies get blamed, not them.