This has been my introduction to Robb's writings and I must say, I'm impressed. From the blog

Iraq's state is hollow -- it exists but without any meaningful functionality.... A hollow state doesn't provide the first two layers, which by extension makes the layers above it inconsequential (contrast this to the US strategy for Iraq). These services, to the extent that they do exist, are being supplied by black markets (from gasoline to the 2 MW ad-hoc electricity network in Baghdad) and neighborhood militias. In order to get these services, the population has replaced any residual loyalty to the state with primary loyalties (to tribe, family, mosque, religion, gang, etc.).

Now that this transition to primary loyalties is complete, the feedback loops of ongoing decentralized conflict ... and large scale systems disruption ... will ensure that it stays that way. Also, the alternative transnational market structures of black globalization, driven primarily by the smuggling of hundreds of millions of dollars in bunkered fuel every month, will provide much of the fuel to keep this situation going.

Robb provides a different view of the dissolution in Iraq. The conventional wisdom is a Shia'/Sunni civil war. But Robb both here and in the essay, sees a highly fragmented but efficient set of groups [the open source war cemented by a primary loyalties in a decentralized conflict] operating independently but making marriages of convenience to cooperate when it's in everyone's self-interest. And, from the essay...

Indeed, because the insurgents in Iraq lack a recognizable center of gravity--a leadership structure or an ideology--they are nearly immune to the application of conventional military force.

I respect Robb's arguments but still think the primary loyalty is religious sectarianism. Recent events following the destruction of the sacred mosque

The nature of the Iraq war has been changing since at least the late autumn, when political friction between Sunni and Shiite Arabs rose even as U.S. troops began carrying out a long-term plan to decrease their street presence. But the killings accelerated after the bombing on Feb. 22 of a revered Shiite shrine.... ... that Sunni-Shiite tension sharpened when insurgents destroyed the golden dome of the Askariya shrine in Samarra in February and vengeful Shiite militiamen rampaged through Baghdad and other cities.

There's no doubt that a free-for-all is still in place with little intra-sect discipline. There are a number of Shiite political parties who must agree to unify their political block in any new government. One is led by Moqtada al-Sadr

who seems to be operating independently of the Grand Ayatollah Ali al-Sistani or incumbent prime minister, Ibrahim al-Jaafari. From the NY Times Iraq's Premier Is Asked to Quit as Shiites Split

Any dispute between the Shiite bloc's two biggest factions -- Mr. [Abdul-Aziz] al-Hakim's party, the Supreme Council for the Islamic Revolution in Iraq, and the party led by Mr. Sadr -- carries with it the possibility of armed violence. The factions are longtime rivals, have backing from Iran and operate militias with members in the Iraqi security forces. Their militias fought street battles last August throughout Baghdad and the south, even hijacking double-decker buses to storm office buildings.

Robb's view is true as far as it goes but I don't think its the end of the story. The greater conflict with the Sunnis could escalate, which would unite all now disparate groups along sectarian lines.