"The first instructive set of data comes from the U.S.-sponsored Radio Free Europe/Radio Liberty. In March, the organization analyzed the online postings of eleven prominent Sunni insurgent groups, including AQI, tallying how many attacks each group claimed. AQI took credit for 10 percent of attacks on Iraqi security forces and Shiite militias (forty-three out of 439 attacks), and less than 4 percent of attacks on U.S. troops (seventeen out of 357). Although these Internet postings should not be taken as proof positive of the culprits, it's instructive to remember that PR-conscious al- Qaeda operatives are far more likely to overstate than understate their role.
"When turning to the question of manpower, military officials told the New York Times in August that of the roughly 24,500 prisoners in U.S. detention facilities in Iraq (nearly all of whom are Sunni), just 1,800—about 7 percent—claim allegiance to al-Qaeda in Iraq. Moreover, the composition of inmates does not support the assumption that large numbers of foreign terrorists, long believed to be the leaders and most hard-core elements of AQI, are operating inside Iraq. In August, American forces held in custody 280 foreign nationals—slightly more than 1 percent of total inmates."
So why does the US portray them as this hugely monumental group that's causing all sorts of trouble in Iraq, making it appear that "If we can just take them out, everything will improve!" Andrew Tilghman goes through many very good reasons why and, when he gets to how AQI might be benefiting from other players in Iraq talking them up, he reminds me of the story of Rose O'Neal Greenhow, a Confederate spy in the US Civil War. Greenhow made extravagant claims for how much information she was able to transmit to the Confederacy, but no one questioned her claims until a decade or so back. I remember reading that Greenhow exaggerated her role simply because it pleased her to represent herself as a dramatically capable spy. The fellow who broke the case, Allen Pinkerton, also had a motivation to exaggerate her role as he had just taken over the newly-formed Secret Service right before catching her. He cheerfully collaborated in building her legend as, having been the one who caught her, that made him and his new organization look all the more competent and effective.
In much the same way, Tilghman reveals that there are many players in Iraq who benefit from the appearance of a powerful and effective AQI. It's quite clear that AQI will remain in Iraq as long as the Americans remain. The author is of the firm belief that AQI will leave Iraq shortly after the Americans do as 1) Iraqis will have no reason to want to keep them around and 2) They simply aren't powerful enough to remain at large and independently operating once their reason for being there disappears.
The article is well worth reading for the many insights into the insurgency and how US forces are dealing with it.