There is no doubt about the importance of social media in organising and directing crowd behaviour. But there has been little discussion of how these models maintain certain social structures outside of periods of group activity.
As far as I can see, in the case of the London riots, young people are so intertwined with online social networking that they are never disconnected from the crowd. The ideas that seem ‘normal’ and ‘acceptable’ during the actual riots – vis a vis hatred of the police, the desire to burn down and loot property – are maintained through these online connections. When otherwise people may have had time to individually draw stock and reflect, there is always the online ‘crowd’ continuing to stoke the fire.
So, naturally then, people get together under the excitement that something might happen. And when inevitably something does kick off, everyone gets involved. What we then have is chaos and typical rioting behaviour.