Why do riots spread as they do?

[corncrake]

I live in one of the other smaller cities that decided to join in after the london riots and the people who were silly enough to act up were just trying to get in on the action so to speak like boasting or trying to look hard. I don't think the triggers are as straight cut as believed (the rebellion against poverty etc) as it becames pretty obvious that the original flash point in london (a peaceful march against the police) was hijacked by a minority hellbent on causing trouble totally opposite of the aim. These people then spotted the police's inaction and vastly undermanned opposition took to facebook,twitter and the totally private blackberry message system to call for backup out pacing the police everytime.

They did'nt just randomly roll through areas they selected the more attractive ones (high streets,malls etc) then moved on to the next loot spot when it had been stripped. Mob mentality (the sense of getting away with it because you know you are in a crowd so no can tell who did what?) kicked in but in the aftermath i guess their greed and ignorance was their downfall as pretty most of their targets had high grade cctv and their communities literally openly defied them by coming together in some places and helped each other clear up and spoke to each other in reaction to the situation.