Spontaneous, creative protests organised using social media

At the moment there are a number of protests going on around the UK after it emerged that mobile phone company Vodafone had been let off a £6 billion tax bill.
The story is interesting for a number of reasons but what I want to focus on is the way it demonstrates social media can be used to raise awareness of an issue and organise support.
There was some reporting of the story back in September by Private Eye, a satirical political magazine and by the This is Money website: http://www.thisismoney.co.uk/news/article.html?in_article_id=514832&in_p... but it was only when a journalist, Johann Hari mentioned it in an article about the unfairness of the cuts in the UK that people really began to take note of it.
You can read that article here http://www.johannhari.com/2010/10/21/britain-just-became-a-colder-cruell...
Soon people were asking on Twitter if the story was true, while others were passing on links to articles.
A tweet demanding the mobile phone company cough up received 1,952 retweets, ranking it as the 6th tweet in the world on Twitoaster.com having reached 400,000 accounts.
In the week that followed there were a number of protests outside Vodafone stores around the UK.
In his column (http://www.independent.co.uk/opinion/commentators/johann-hari/johann-har...) a week later, Johann Hari wrote:

Many people emailed me saying they were outraged that while they pay their fair share for running the country, Vodafone doesn’t pay theirs. One of them named Thom Costello decided he wanted to organize a protest, so he appealed on Twitter – and this Wednesday seventy enraged citizens shut down the flagship Vodafone store on Oxford Street in protest. “Vodafone won’t pay as they go,” said one banner. “Make Vodafone pay, not the poor,” said another.

Although the story was reported on a credible site, the government has dismissed the claim that the figure was £6 billion as an “urban myth”.
We will have to wait and see what happens next but it does show how social media can be used to draw attention to an issue and mobilise support. I would like to hear any other stories about using social media to inform people and campaigns.