Here's David Cameron on 22 February  in Kuwait, talking up the power of social media in the wake of the nascent Arab Spring:
[The movement] belongs to a new generation for whom technology - the internet and social media - is a powerful tool in the hands of citizens, not a means of repression.
And here's Cameron on Thursday 11 August  talking up the perils of social media in the wake of the English riots:
Mr Speaker, everyone watching these horrific actions will be stuck by how they were organised 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.
(Hat-tip: @wblau )