well ok, enough about the weather, although rain is the policeman's friend, I've heard.
I think the difference is cultural.
I think the riots are an extension of a certain culture in England - it's a manifestation of a certain culture and therefore a political act. And these people are the product of society in major cities of England. And yes loads of 'educated' and professional people will join in for the buzz of it but there are many, many who are young and feel disenfranchised.
They know they are poor (it's all relative) - they have insight into their situation - and they are unlikely to ever achieve the sort of lifestyle that is dangled in front of them in music videos and on the TV.
In London and other big cities, you don't know your neighbour, people fuck you over in small ways and big, there is no sense of belonging, no community leaders and you think, why not just take what I want?
The basis for group conflict is inequality, one perceived group fighting for to show power and status against another 'group'. Smashing up/stealing another group's status objects is showing power and acquiring status.
I know this sounds liberal and wanky but I don't think just saying oh they're 'bad' is frankly good enough.