"Rioting" in Rome is like professional wrestling in the U.S. . .fake but still dangerous.
How is it fake? You have to keep in mind that Italy is a wholly owned subsidiarity of labor unions. So, when the transit workers' unions "riot," they are met by the public safety workers' union (i.e. the cops). In some ways this is a good arrangement b/c the violence btw Rioters and Cops tends to be relatively low-key. Watch a few videos of recent Roman riots and notice that the cops go out of their way not to get too rough. The same courtesy is extended from the other side. Usually you get some tear gas, a few night-stick injuries, some minors cuts. . .nothing too serious. Back in Dec. 2010 it was obvious from news video that neither the protesters nor the cops were much interested in a clash. Both sides advanced and retreated when necessary to avoid excessive violence (02:00).
Despite the unspoken agreement not to let the violence get too serious, individuals and radical groups do cross the line and people get genuinely hurt and even killed. Yesterday's violence in Rome is an example of this. An otherwise routine Saturday protest was infiltrated by the so-called Black Bloc Guerrillas (those guys in the black masks and helmets). This group's only purpose is property destruction. Burn a few cars, break a few windows, dump garbage on the street. Yesterday some of them got inside St John Lateran and made some noise. They broke a statue of the Blessed Mother outside (00:30). I doubt that they set out to kill anyone, but burning cars in the street often has unintended consequences.
Professional wrestlers in the U.S. often get hurt and sometimes even killed. But the whole performance is carefully choreographed and managed. Before the manifestazioni take place, notices are placed in all the major newspapers letting folks know when and where things will likely get rough. Lists of potentially stalled bus and metro lines are published. The police are out early to block streets and corral pedestrians. Helicopters are sent up to watch over the protests. Media types are given notice so they can get their pics and vids for the news. It's all very civilized.
So, what's my point? Protests and riots in Rome are a form of public performance art. A distraction that sometimes gets a little out of hand. They do not express a general unhappiness with the State nor do they lead to fundamental political change.