With social media brutally accelerating the news cycle and allowing rumors from riots to bank failures to spread at lightning speed, politicians, businesses and governments must adapt fast.

Thursday, British Prime Minister David Cameron threatened to temporarily block platforms such as Blackberry messaging used to coordinate looting and unrest -- but the experience of the Arab Spring suggest that approach might be doomed to failure.

For some of the world's most powerful countries, the stakes could hardly be higher. Britain's riots rendered parts of London and other cities briefly ungovernable and raised serious questions over the sustainability of the government's austerity strategy.

The ousting of presidents in Tunisia and Egypt by social media-fueled revolutions clearly alarmed China's rulers, who rely on a sophisticated system of networked authoritarianism to control online debate and avoid a similar fate.

But even some veteran security specialists warn such attempts may not only be doomed to failure but could jeopardize the authority of those who try. Egyptian President Hosni Mubarak's Internet shutdown, they warn, merely served to bring more people onto the streets.

The use of social media in the unrest looks like a game changer but any attempt to exert state control... looks likely to fail, said John Bassett, a former senior official at British signals intelligence agency GCHQ and now a senior fellow at London's Royal United Services Institute.

Ultimately those governments that try to operate old-style control models are likely to fail, losing legitimacy and respect in the eyes of their populations,

Monitoring networks for useful intelligence was useful, he said, as was encouraging individuals and community groups to report potential troublemakers.

But most communication experts say that what established organizations really need to do is learn to use such platforms to shape the narrative themselves. And they need to learn fast.

Caroline Sapriel, a specialist consultant based in Brussels who advises multinational companies on crises, says the key is for firms to use platforms such as Twitter to swiftly engage on an issue and avoid losing control.

LIGHT-SPEED CRISES

These days, crises of all types unravel and gain momentum at light speed, she said. There is no longer any question that to tell your side of the story... social media is the way -- not reactively but proactively, strategically planned and handled by specialists around the clock. This is not a part-time job.

Rupert Murdoch's News Corp discovered that to their cost last month. An online Twitter campaign to persuade advertisers to abandon the scandal-hit News of the World took hold so fast that the paper ceased production within days.

Allegations that the newspaper hacked telephone voice mails and paid for police information not only inflicted lasting reputational damage on News Corp but also much of the British establishment seen as much too close to mogul Murdoch.

With financial markets more volatile than ever, that is a point banks in particular might need to take on board. This week, just as during the 2008 crash, banking shares in particular have seesawed violently on rumors that the institutions themselves were often far too slow to deny.

It is also a learning curve that some British police forces have clearly struggled with, particularly London's Metropolitan Police -- perhaps because several senior officers quit last month following the News of the World scandal.

Other forces such as those in Manchester were much quicker to use Twitter to engage with residents, also posting images of looters on Facebook for members of the public to identify.

Captured lots of criminals on CCTV -- we will identify you and will be coming for you, said one message.

MAKING POLITICAL CAREERS?

Whilst many British politicians -- including Cameron, on holiday in Tuscany -- were notably silent on social networking sites in the early days of the riots, a handful were praised for using it very successfully.

Twitter is really proving itself to be key here, said David Lea, Western Europe analyst at Control Risks. It's a way of being seen to do something, if nothing else. There are MPs building reputations and careers with it.

Northeast London lawmaker Stella Creasy knocked down rumors of disturbances in her constituency, reporting what was really happening, coordinating community relief efforts and trying to deter vigilante action.

If you want to help the police, ask the police how you can help, she wrote in a public message to one constituent. Running about with baseball bats and hype isn't helpful.

In another message apparently written from inside the House of Commons chamber Thursday, the opposition Labor MP said blaming Twitter for the riots was bonkers.

That view also looked to be shared by at least some members of Cameron's ruling Conservative party, clearly already worrying that threatening effective censorship could be a colossal political mistake.

Platforms like Twitter helped residents and police track the problems and maintain contact with services, said one Conservative aide, warning that how Cameron addressed the riots could define the rest of his time in office.

This could be either his Katrina or his Falklands.

(Editing by Sonya Hepinstall)

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