On 15 June 2009, while thousands of Iranians were streaming on to the streets of Tehran to protest against the disputed results of the presidential election, Jared Cohen, an official in the US state department, quietly sent an email to Twitter. Despite coming from the youngest member of America's foreign policy arm – Cohen was just 27 at the time – it was surprisingly serious. Cohen wrote that, in the view of the Obama administration, Twitter was playing a crucial role in Iran as a way for protesters to communicate. He implored the social networking site to delay routine maintenance work it had planned for the following day that would have brought down all its feeds in Iran and possibly disrupted the organisation of the protests. Twitter complied, putting off the maintenance for 24 hours, thus allowing the flow of tweets to continue uninterrputed. The demonstrations grew and grew.

At face value the exchange was harmless – an example of government and business working together to forward America's interests abroad. But in the eyes of one scholar, this apparently benign interaction was to have powerfu, unforeseen consequences. In Evgeny Morozov's analysis, Cohen's email set a dangerous precedent, convincing the Iranian leadership, and many other authoritarian regimes around the world, that the US government was in cahoots with Silicon Valley and that the internet was being turned into an extension of politics by other means.

Morozov, a visiting scholar at Stanford University in Palo Alto, followed the fallout in Iran, Russia, China and elsewhere, and was alarmed by what he saw. "The email was taken as evidence that the US government was behind the protests, and that in turn was used to portray all Twitter users in Iran as agents of the west. People who were blogging about cappuccinos found themselves transformed into Lech Walesa."

Digital retribution was swift. The jails began to fill.

Morozov is fast becoming a leading voice of what might be called the cyber-sceptic school of internet studies, at a time when such views are becoming more fashionable. After so many grand predictions have been made about the world-changing potential of Twitter and Facebook, the backlash has set in, with pundits now questioning whether the web is all it's cracked up to be. Take Zadie Smith, for example, who recently wondered aloud in the New York Review of Books whether social networking is creating a generation of People 2.0, or Malcolm Gladwell who cited Morozov in a New Yorker article in October that cast doubt on Twitter and Facebook as instruments of genuine change.

Morozov's status in this burgeoning camp of sceptics can only be enhanced by his new book, The Net Delusion, which chronicles what he sees as the inflated hopes invested by the west in the internet and the damage that has been caused as a result. Yet he cuts an unlikely figure for someone playing a central role in an increasingly vital debate about the place of social media around the globe.

For a start, there's his age. At 26, he's even younger than Cohen was when he fired off that fateful email. And then there's his background. Far from the twin Meccas of new technology – northern California and New York – Morozov hails from a small potassium-mining town in Belarus. His parents worked for the mining company, as did everybody else in Soligorsk (which translates as "mountains of salt"). "I know more about potassium than I like to admit," he says.

But it's precisely his decidedly old world, highly ungeeky, roots that make Morozov a credible observer of the west's uses, and abuses, of the internet. They give him an affinity with those who live under authoritarian regimes, having grown up in Belarus, which Condoleezza Rice once described as the last outpost of tyranny in Europe.

As we sit and talk in a cafe near Capitol Hill in Washington, Morozov admits rather sheepishly that in the beginning he was himself a passionate believer in the democratising potential of the web. After school, he moved to Bulgaria with the benefit of a grant from George Soros's Open Society Institute and then worked for an NGO in Berlin. He even become one of the first to use the term "Twitter revolution" at the time of the protests in Moldova in April 2009.

"It was hard not to be infected by a sense of optimism and excitement about the freedom agenda that was around at that time. I genuinely thought it was making a difference. Democracy appeared to be advancing and marching, and the web 2.0 seemed to be part of it, bringing people on to the streets."

The doubts set in, tentatively at first, with Moldova. After the protests ended, it transpired that there hadn't been that many Twitter users in the country, and that other forms of communication – including the good old telephone – had been just as important.

Then when Tehran erupted, Morozov had a deepening sense that the claims being made for the internet as a pro-democracy force were being wildly exaggerated. In his book, he points his finger at those he accuses of hype, or as he puts it "cyber-utopianism" such as New York University's Clay Shirky – "this is it, the big one, the first revolution transformed by social media" – Mark Pfeifle, a former George Bush adviser who tried to get Twitter nominated for the Nobel peace prize, and our friend Cohen again, who called Facebook "one of the most organic tools for democracy the world has ever seen". The Guardian also gets a name-check, with Morozov referring to an op-ed that proposed to "bomb Iran with broadband".

The more he looked into it, the more he came to the conclusion that western views of social networking were hopelessly naive and out of kilter with the realities on the ground. "Because of cyber-utopian ideas, for the past 10 years the west has failed to think about how to use the internet to its best advantage," he says. "Instead of really thinking about how to address these issues, we have spent too much time extolling the power of Silicon Valley to conquer authoritarianism simply by opening offices in Vietnam or China."

That failure has allowed authoritarian governments to develop their own presence on the web, to powerful effect. Initially, the techniques used were blunt and unsophisticated, such as the Chinese government's decision simply to turn off the internet for 10 months in 2009 amid the growing unrest in Xinjiang. But over time dictators and oligarchs have become adept at fine-tuning their methods. "Western analysts have underestimated the degree of customisation that censorship now takes. It was thought it would be a matter of banning the internet, but now you can ban from it only those people who have human rights activists as their Facebook friends or have downloaded at least five New York Times articles. It's this kind of customisation that allows economies to keep growing while making sure that their opponents only have access to the domestic internet and not the global one."

Morozov deploys a host of examples to make the point that anti-democratic forces are becoming savvy at manipulating the web. Take Konstantin Rykov, who in the late 90s was in the vanguard of Russian internet entertainment-slash-porn having been one of the founders of a website with the suggestive name fuck.ru. Now he is an internet adviser to the Kremlin, and spends his energies putting out pro-Putin propoganda.

Or Hugo Chavez, one of America's most devoted irritants, who responded to the Venezuelan opposition's use of Twitter by setting up his own Twitter account, which in less than a month acquired 500,000 followers. Or China again, which has created a mammoth network of pro-government internet commentators, known as the Fifty-Cent Party after the amount they earn for each favourable post. One estimate puts their number at 280,000. Or, for that matter, Iran, which saw a 200-fold increase in the number of pro-government tweets once the so-called "Twitter revolution" began.

Morozov ridicules the inadequacy of the west's approach to the internet, but he reserves his greatest scorn not for Washington's incompetence – though he suggests there is plenty of that – but for its hypocrisy. While Hillary Clinton at the state department was busily promoting the cause of "information freedom" around the world, as she did in a much-vaunted speech last January, domestically the US government has been scuttling in the reverse direction.

"The director of the FBI has been visiting Silicon Valley companies asking them to build backdoors so that it can spy on what is being said online. The Department of Commerce is going after piracy. At home the American government wants anything but internet freedom," he says.

And then, along came WikiLeaks, putting an end to any lingering uncertainties about the US government's true intentions. Not only did Washington's response to the embassy cables blow asunder any claims it had to be a supporter of "information freedom" – Morozov doesn't expect Clinton to give another speech on the subject for quite a while – but it also reinforced the over-cosy relationship between government and Silicon Valley when Amazon, Paypal and other firms heeded the government's calls and sent WikiLeaks into the wilderness.

Like Cohen's original email, Morozov believes, there will be consequences to such actions. "More and more governments will now see American technology as political – as putting the interests of the US ahead of any others."

There is a personal danger involved in sounding the alarm on the direction of the internet, as Morozov does. For one so young, isn't he running the risk of sounding like one of those crusty old refuseniks who just don't get the internet?

"There is currently a popular discourse that bashes the internet for destroying culture or privacy, and I'm often lumped in with that, which I don't enjoy. But people who know me and my work, know that I'm very much involved in trying to understand how to use the internet to promote democracy. I haven't given up on technology, but I do believe it needs to be done differently."