Blame him for what? The Federal response was right on par with all previous responses to hurricanes. Basically this guy got slimed for not responding quickly enough to an unprecedented natural disaster that was further blown out of proportion by the failures who make up the mainstream media. Almost all of the hysterical coverage in the days following the hurricane (which was when Brown took the most heat) turned out to be bullcrap.
Basically the main thing this guy did wrong was not turn into Superman, fly around the world to turn back time, and then visit NO to tell Nagin and Blanco to get their sh-- together. And, yes, I do hold him accountable for not doing that.