Sao Paulo (where I ... erm ... was thinking of moving to) explodes.

The beeb has a quick overview of the gangs. Including the PCC which apparently started as a prisoners' defence movement after (presumably, although not specified by the BBC) the Carandiru massacre. It's worth watching that film to get an idea of Brazilian prisons.

That emphasis on the interaction between political and criminal activity is important. It is the "Global Guerrillas" analysis (which I referenced in my discussion of the Euston Manifesto) You'll misunderstand the whole thing if you see "islamism" as some kind of sui generis unique evil. What we're seeing is the switch in people's loyalties and sense of who they are, to their membership of religious sects, tribes, gangs etc and away from their loyalty to the nation-state. This happens when the state is either a) repressive to this group, b) too weak to provide the group with the security it needs or c) the group are immigrants from another culture who have difficulty assimilating.

That's not new. There have been epochs of warring "gangs of New York" of ethnic Irish, Jewish and Italians. It's not new that such gangs are started with a mixture of community defence vigilantism and other political ideals, but soon extend the violence and adopt crime as tactics for financing themselves, protecting their own integral structure and the positions and lifestyles of their leaders.

What's, maybe, new is the degree of empowerment that new technologies like cell-phones bring. And also, the degree of spontaneous / opportunistic co-operation and information sharing between different groups. Criminal gangs in Haiti have copied the beheading tactic of Iraqi groups. Nigeria has car-bombs. In Rio, gangs pioneered the burning of busses with their passangers on-board. Although, thankfully, this doesn't seem to have been repeated in Sao Paulo (yet).