Can the microblog change the megastates? In China and India, social media is leapfrogging official and mainstream media narratives, giving voice to the wants and frustrations of the new middle classes.

But it is also helping to expose stark differences in the nature of the political systems of the two Asian giants. Differing official responses are leading to very different political impacts. Indeed, it could be that social media ends up affecting the future of China more than it does India.

Perversely, the potential power of social media within the People’s Republic of China can be measured not so much by what it says as by what it is forbidden from saying. If the Communist Party sees fit to go to the trouble of banning certain words on the wildly popular microblog Weibo—which has more than 300 million registered users—then one can assume there is no small number of people wanting to express them.

And if anyone wants to invest the time in comprehensively testing Weibo for blocked words, a fascinating and disturbing picture emerges. The team at China Digital Times, a student-run initiative at Berkeley, use crowd-sourcing to provide precisely that service.

On 4 June this year, for instance, China Digital Times revealed that the following search terms, among others, were blocked on Weibo: fire, candle, blood, people, movement, crush, tank, 8, 9, 6, 4, 23, 35, anniversary, today, yesterday, tomorrow, that year, declaration, commemorate, monument, park, recall, mourn, silent tribute, evening event, black clothes, go into the street, and never forget.

These are just some of the terms deployed by Chinese social media users to mark the anniversary of the murderous suppression of the Tiananmen Square protests in 1989. And these are just some of the coded ways used to circumvent the bans on more direct expressions of remembrance and outrage. Especially surreal was the banning of the normally harmless candle emoticon on Weibo, with queries receiving the less-than-reassuring message: “the related icon is currently being optimised”.

To be sure, banning everyday words and icons is not a sustainable social media policy, and many of the aforementioned search terms probably started working again within a few days of the anniversary. The curbs on Weibo, it seems, are a moveable famine. At times, for example, you may also have trouble finding the combination of “Ferrari + car crash” or, even more intriguingly, “high speed + car sex”. Which only begins to make sense in light of a mysterious car accident in Beijing on 18 March, and rumours about the son of a high-ranking official.

Taken together, all of these omissions reveal not only some of the things that the Communist Party does not want people to know. They also illuminate the Chinese genius for allusion. If there are so many ways to bypass crude official censorship, then the wholesale suppression of truth looks set to be a losing battle.

Block one way of expressing a sensitive point and sooner or later someone will find another. And each time one of China’s hundreds of millions of ordinary non-political social media users finds a seeminglyinnocuous turn of phrase blocked, the aggregate of frustration with the Chinese Communist Party’s current style of governance will rise by one infinitesimal increment.

In India’s democratic tumult, meanwhile, social media provides a more forthright avenue for political grievance. Facebook, Twitter and local variants are having a marked impact on the political debate, from calling for security reform after the 2008 Mumbai terror attacks to castigating the soft-power failures of the 2010 New Delhi Commonwealth Games to keeping the heat on corruption.

Notably, India’s social media scene is now pressuring the mass media, especially newspapers, to reduce self-censorship when it comes to reporting corruption and failures of governance. India’s professional journalists may take pride that their craft is a mainstay of the world’s largest democracy. But in a ruthless commercial environment, mainstream media organisations also tend to sniff the political wind before they decide how to report it.

A watershed moment came in late 2010, when sustained agitation from Twitter users pressured newspapers into finally reporting a story that had been brewing for weeks. This involved the alleged connections between some prominent journalists and a lobbyist who in turn was under scrutiny for her part in an alleged corruption scandal over the allocation of telecommunications spectrum rights.

In one sense, social media can be a new equalising force in an India long-criticised for perpetuating inequality alongside democracy. It tells you something about modern India when outspoken young novelist Chetan Bhagat (@chetan_bhagat) has around a million Twitter followers—eight times as many as Prime Minister Manmohan Singh (@PMOIndia).

But in India’s political cacophony, Twitter and its ilk do not just serve those who would speak truth to power—these are also platforms for those who possess power or seek it, whatever their chosen means. Thus you will find blogs supporting India’s armed Maoists as well as the tweeted thoughts of political players ranging from Gujarat Chief Minister and controversial Bharatiya Janata Party figure Narendra Modi (@narendramodi) to former senior UN official, author, minister of state and irrepressible congress parliamentarian, Shashi Tharoor (@ShashiTharoor).

But their audiences, however disparate, are still in the minority: literate, internet-connected, often English-speaking. Hundreds of millions of Indians may now use mobile phones, but so far only tens of millions use social media.

For the time being, the silences on Weibo will continue to ring louder than all of India’s social media din.