For all purposes criminals. There's nothing in these riots about lack of jobs, police brutality or social injustices. If anything they are just demonstrating why we have governments, why police is constantly on the edge and why they can't get a decent job.
Now, don't think for a moment I'm against violence. Here's the shocker; I'm not! It can be said with a fair amount of truthfulness to it, our civilization has evolved through the act of violence. Revolutions, civil wars, rebellions, riots, war itself, while destructive forces, have often been the at the source of great things. But alas, there was no protest here. No marching of the population with a common goal that eventually lead to violent disturbances. A situation that could, in some way, legitimated violence. It would be, of course, left to be seen exactly what type of violence and what exactly would these people be protesting about. Rampaging against police stations or governmental institutions would represent the form of protest that could indeed signify a true feeling of injustice by the rioters.
Destroying historic buildings, the livelihood of middle and lower classes,
robbing injured people on the street, ransacking, does not. It's just a repeat of the Paris riots, some years before.
As for social networks... I wouldn't go as far as compare governmental position in Iran and Egypt with Britain. The first two were true population revolts with a well marked political motivation. That's the type of protest where I can see violence being legitimated. Our democracies were built this way (and have evolved this way). In London there's just and only criminal behavior being -- apparently -- organized through social networks. Certainly I agree these shouldn't close. But if, and ONLY if, these companies cooperate with authorities in catching the perpetrators. This can become a very dangerous world otherwise.