I think this gloom and doom talk is a bit premature. That city may be more resilient than it now appears, in a few months when the 75% of the population who evacuated are able to return and start rebuilding their lives.
Probably any major metropolitan area would show a similar reversion to animalistic behavior when disaster strips away the thin veneer of civilization and only the poorest and most ignorant are left behind. New Orleans is not special in that regard.
I agree though that developers will blanch at rebuilding some areas. When I see the sea of rooftops poking through the water on TV, I wonder how many of those structures will still be viable when the waters subside? I bet they end up having to bulldoze whole neighborhoods.