England’s Prime Minister David Cameron addressed the House of Commons today in the wake of the recent riots in that country. He noted how social media sites were used to organize protestors and rioters and says he’s looking in to whether the sites could be blocked for certain people:

Mr Speaker, everyone watching these horrific actions will be stuck by how they were organized via social media.
Free flow of information can be used for good. But it can also be used for ill.
And when people are using social media for violence we need to stop them.
So we are working with the Police, the intelligence services and industry to look at whether it would be right to stop people communicating via these websites and services when we know they are plotting violence, disorder and criminality.

Some arrests have already been made of people accused of trying to incite violence through Twitter or Facebook in Great Britain.

A recent poll in England found 38% of Britons support the idea of shutting down social media during civil unrest.

Elsewhere in England, a 21-year-old club DJ in Bristol on a fixed gear bike has emerged as a leading citizen journalist. He traverses the city offering detailed reporting on Twitter about what’s going on.