Surge, Success or Not mentioned the walls dividing Baghdad communities, and asked the question re how sustainable current reductions in violence are given a) these walls can not be permanent and will be coming down at some point, b) that some of the four million plus internally/externally displaced people might return to the homes from which they were driven, c) that some of the current measures being taken (see the Gen. Odierno article) also have to be eventually relaxed, etc, etc. Here are pictures of the wall between the Ghazalyia and Shu'la neighborhoods, and the wall surrounding the Adhamiya neighborhood. Articles (pro & con) linked below.
In defense of Baghdad's 'walls'
Why Walls Don't Work in Baghdad
Baghdad Walls Key to Baqubah Push?
Baghdad Walls Divide Neighbors, Friends
In pictures: Baghdad murals
And the link below has an explanation by David Kilcullen, the Senior Counter-Insurgency Advisor, Multi-National Force -- Iraq. Note: even he says that "The security controls are not permanent, and can be readily removed when the situation improves." The Urban Tourniquet - "Gated" Communities in Baghdad