This headline makes me think of something I've been thinking about for some time -- the huge divide in the American left between Anarchist radicals (like those accused in this case) and everyone else. It is a divide that encompasses the difference between violent rioting (or even terrorism) and non-violence, but it goes much deeper, into the fundamentals of the ideology.
Put simply, there is no 'American Left' but a mish-mashed collection of the 'Progressives' (those to the left of Obama, lets say) and the 'Revolutionaries', who are mostly anarchists of some stripe. The 'Progressives' believe what most liberal democrats do, just more so. They want single-payer healthcare, strong environmental protections, more equality for women and minorities (via non-discrimination enforcement and other means) and that sort of thing. If you were to turn the Democratic party's platform up to 10, you'd get at what they believe. The Revolutionaries, on the other hand, want to dismantle capitalism and the American system of government. They don't want single-payer healthcare or other governmental programs, but either a collection of anarcho-syndicalist collectives or primitive tribes. Not surprisingly, the progressives generally prefer the electoral process and peaceful protest and the revolutionaries are more willing to embrace violence. The violent ones seem to be a fairly small minority of the Revolutionary Left in America, but in the end the only difference between a nonviolent anarchist and a violent one is which one is holding the molotov cocktail (this is, needless to say, a big difference); theirs is only a disagreement about tactics. Progressives, on the other hand, disagree with revolutionaries about just about everything.
Consequently the Progressives and Revolutionaries do not share objectives or even tactics. The former want to reform the system and get like-minded people elected, the latter want to tear the whole system down and start from the ground up. All they share is similar targets for their anger -- corporations, the wealthy, war, environmental destruction etc. For the past decade and more these shared targets have repeatedly put progressives and Revolutionaries side by side, first in the anti-globalization movement, then in the protests against the Iraq war, and now in the Occupy movement. The Radicals are generally more dedicated, and provide the organizational structure and the footsoldiers for a lot of these movements But this has never been an easy coalition, and the fault lines are pretty obvious.
In the end these fault lines may be why the American left cannot exert the pressure that the right does. In the end, most of the far right in America agrees with much of the Republican party platform, but radicalizes it. Even hard-core racists generally do not reject the American system of government, rather they want to exclude all brown people from it. Conservatives and militia types can agree about the evils of Affirmative Action, Abortion, Taxes, immigration and government programs to help the poor. In general, the American right is united in its belief that government should not be helping the disadvantaged and that taxes should be low. On an organizational level, Ron Paul can use white-supremacist mailing lists and Republican politicians can draw support from groups like V-Dare and the Conservative (White) Citizens councils. The far right is as fervent as the radical left, but unlike them it is pretty passionately involved in partisan politics. Consequently the right can draw strength from its fringes, because there is a broad agreement about their general objectives and a great deal of organizational cooperation between the fringes and the mainstream.
In contrast, the left is divided, which goes some ways toward explaining why Occupy has yet to turn into a left-wing tea party.