Of course, I realize that, in a large city like that, getting out may not be so easy, and that some people don't own cars, etc. But, for the rest, what tends to happen in areas that are threatened by a recurring danger like this (after all, there are hurricanes every year in the gulf), people get complacent. They've lived through them before, and figure they can do it again. And who wouldn't prefer sit it out at home rather than huddle in a shelter? Nevertheless, sitting it out is a very bad idea when things are dangerous enough that a mandatory evacuation is declared.
Another thing that happens whenever we have a flood is that people go sightseeing, and they drive straight through flood water -- many times getting themselves stuck requiring some brave cop or national guardsman to rescue them. (Safety Rule: Never drive your car through flood water, it could be swifter and deeper than it looks. Especially never drive around flood barriers.) People indulge in the same kind of stupidity during hurricanes -- the news reported people taking their kids out to see the waves, taking pictures, etc., as the storm moved closer.
Speaking of the National Guard, those guys have my deepest respect. Even when we choose to sit out a flood, it gives me a great sense of security seeing those big trucks chugging through the flood water, knowing help is close by if it should become necessary. Right now, they are out there risking their own lives to save others; they are heros and deserve our thoughts, prayers, and support.
In fact, some prayers in general would be appropriate now. Whatever my impatience at folks who didn't heed the warnings, *nobody* deserves to be suffering what tens of thousands are now suffering down there.
Additional thought: As I watch this massive effort to evacuate the entire city of New Orleans, I can't help but wonder why there wasn't a more organized effort to get people out beforehand. They knew that many of the city's poor didn't have the means to leave -- and it certainly is easier to evacuate people ahead of time than it is when there is water all over the place!