It looks bad for the greens in Iran, silent sitdown strikes that were really working have now turned to rock throwing and fires.  Are violent factions in the protest movement being encouraged by government provacateurs?

That is my guess, anger is taking over.  Government thug handlers are sending them out to act like angry protestors giving police and militia the excuse they desire to attack en masse and then murder innocent nonviolent protestors in the crowd with rooftop gunfire.

When nonviolent protestors are murdered in this cowardly, psychotic fashion, already angry, rock-throwing, fire starting protestors become enraged.  The escalating violence will scare the masses that the protest needs to succeeed into hiding.  Only the violent will remain.  Armed with rocks and fire bombs they will quickly be overwhelmed by armed, shielded riot police, and the government will justify this by showing the violent rioting.

Can Mousavvi rein in his supporters now at this late date?  That is highly unlikely.  Can he explain how violence will lose the battle and only nonviolence can win?  Unless he can do this, this fight is very likely lost.  Very sad, but the addiction to anger/fear is strong in the human animal.  This is exactly what tyrants use to control and defeat us over and over again.