Ken Burns in the New York Times discusses reason why the coalition in Iraq did not respond sooner to reports of a Shiite-run torture prison.
He suggests that there were so many different rumors about things going on that the troops couldn't handle them all, and couldn't separate fiction from reality, and so this just fell through the cracks.
I wonder maybe if reports of Sunni Arabs (aka the ethnic group behind the insurgency) being tortured by Shiite Arabs just weren't much of a priority.
Now this is something that if I heard a report that Iran were involved in, I would believe it.
Another interesting note is buried at the bottom of page 2 of the article:
The American command then acknowledged, in the words of one high-ranking officer, that the earlier assessments were based on little more than prideful assertions by Iraqis that their fellow citizens could never do anything so crazy as to blow themselves up, and on "people who came to us after a bombing and said, 'That's not an Iraqi foot,' or 'That's a Syrian hand.'"
I have been operating under the assumption that the insurgency was mainly Iraqi, but that the suicide bombers were mostly foreign. If this is wrong, then it basically shoots to hell the argument that closing the borders between Syria and Iraq and between Iran and Iraq will do much to defeat the insurgency (although even if the suicide bombers are mostly foreign, there is the question of whether they are coming in through Syria and Iran, or through Saudi Arabia). I suppose one could argue that the weapons and cash are coming through those countries even if fighters aren't, but if the suicide bombers are domestic, that would bring into question any part of the insurgency that is supposedly foreign.
That is all.