DC's crisis of 'tonality'
At Newsarama, DC's Dan Didio discusses Identity Crisis, Countdown, and the change in "tonality" of the DC Universe:
When we got Identity Crisis in from Brad, I knew what we wanted to do with the DCU and where we wanted to go. I knew what the tone I wanted to see come into the DCU was – I wanted to put a level of danger and of consequence to the DCU and the characters. We had been addressing that piece by piece, but realistically speaking, you can only change tonality on the individual books incrementally without turning off too many people, or confusing people along the way.
So, when we got to Identity Crisis, and I saw that the story basically hit the nail on the head in terms of the number of characters that we wanted to address as well as changed the whole feel and perception of how people saw the DCU characters – I felt that was a great starting point from which we could move out from.
... A lot of this actually came following September 11th. After everything that occurred in New York City, I was coming to work at DC, and going through the Port Authority. At that time, you would walk into the Port Authority, and you would have National Guardsmen standing there with machine guns. He’s standing there holding his machine gun, and is supposed to be making me feel better and more protected, but somehow, that gave me a greater sense of dread – it put me more on edge.