Mickey Kaus, Matthew Yglesias, Phil Carter and The New Republic's Hassan Fattah have all recently had the same epiphany: that the spontaneous, disorganized nature of the violence directed at US troops in Iraq makes it more dangerous than if it were centrally organized (say, by Saddam Hussein), not less. The justification for this claim is that a centralized guerrilla resistance movement can be crushed by finding and eliminating its leadership, whereas independent bands of snipers can keep popping up indefinitely.
This argument would make sense if the US were planning a permanent occupation of Iraq, and feared losing a never-ending trickle of troops to random attacks. But the American government is at least claiming that its goal is the establishment of a new local government in Iraq. And the threat a centralized underground army poses to the success of this objective is much greater than that posed by scattered anti-American attackers.
An organized guerrilla army, after all, offers an alternative rallying point for disaffected Iraqis unsatisfied for one reason for another with the US Armed Forces' choice of post-occupation government. On the other hand, isolated anti-American thugs on murderous rampages will be more of a law and order problem for the new government than a challenge to their legitimacy or power. And it's not at all certain that they will continue to operate once American troops turn control of Iraq over to a new government and head for home.