In the Guardian today, a first hand account from 'liberated' Fallujah. The concluding paragraph:

The US military destroyed Falluja, but simply spread the fighters out around the country. They also increased the chance of civil war in Iraq by using their new national guard of Shias to suppress Sunnis. Once, when a foreign journalist, an Irish guy, asked me whether I was Shia or Sunni - the way the Irish do because they have that thing about the IRA - I said I was Sushi. My father is Sunni and my mother is Shia. I never cared about these things. Now, after Falluja, it matters.