From: http://www.guardian.co.uk/media/2011/aug/08/london-riots-facebook-twitter-blackberry...

Scotland Yard warned on Monday afternoon that those "inciting violence" on the 140-character social network would not go unpunished. Deputy assistant commissioner Stephen Kavanagh confirmed that officers were looking at the website as part of investigations into widespread looting and rioting. However, the most powerful and up-to-the-minute rallying appears to have taken place on a more covert social network: BlackBerry handsets – the smartphone of choice for the majority (37%) of British teens, according to last week's Ofcom study – BBM allows users to send one-to-many messages to their network of contacts, who are connected by "BBM PINs". For many teens armed with a BlackBerry, BBM has replaced text messaging because it is free, instant and more part of a much larger community than regular SMS.

Seems the tech has raced ahead of the authorities yet again - although not as if equipment manufacturers and operators don't know that there is such a thing as lawful intercept...