From the Counterterrorism blog.

Yet, dropping all pretenses towards brotherly unity, the IAI has suddenly fired off a volley of sullen contempt for Al-Qaida, its Islamic State, and its leader Abu Omar al-Baghdadi--accusing the ISI of spreading "unfair, false accusations" about its would-be connections to the Baath party, threatening other insurgents with death if they refuse to swear allegiance to the ISI, and the fratricide of at least thirty fellow Sunni militants from other groups (such as the 1920 Revolution Brigades, the Mujahideen Army, and Ansar al-Sunnah). The IAI took particular exception to Abu Omar al-Baghdadi's challenge to other insurgents to justify their existence by attacking American military bases: "Oh, forgive us Allah, does this era need further evidence? ...the Islamic Army has executed dozens of raids on bases and military barracks...[including] in the year 2003 before the Al-Qaida network in Iraq was even founded." The IAI even directed an appeal straight to Al-Qaida leader Usama Bin Laden in Afghanistan, urging him to personally look into these allegations and "correct the path" of Al-Qaida's leaders in Iraq.

What does this mean? While it is tempting to think that Al-Qaida may be dramatically losing appeal among Sunni insurgents, one must also be mindful that this new letter may, more precisely, be a sign of a major split within the IAI itself, similar to what has just happened in the 1920 Revolution Brigades. As I discussed in my report State of the Sunni Insurgency in Iraq: 2006, there have long been rumors of such a division within the Islamic Army over the group's relationship with the ISI, particularly in the western Anbar province. Meanwhile, this situation continues to develop, as it is almost certain that the Islamic State of Iraq will soon issue its own stinging digital retort.
To me this is much more significant than the whole Anbar Salvation Council narrative. The Islamic Army in Iraq is one of the major Sunni insurgent groups with a long string of gory videos online to its credit (they're the ones with the black flag mounted on an AK, IIRC). Unlike the ASC, their feud with AQI is untainted in Iraqi eyes by a rush to embrace American military might in Anbar (that the head of the ASC feels the need to have his house protected by an Abrams tank says a lot, IMO). If the split is genuine and not a sign of weakness on the part of IAI, then al-Qaeda's days in Iraq could be numbered.