My understanding is that they are at the point of diminishing returns with respect to search and rescue for people who "demonstrably" want rescue (sitting on rooftops, waving flags, etc). Now they are at the point where they are, for the most part, actively searching for people, with the exceptions being those that may have had a change of heart. I think the forced evacuation order should have been pretty well timed with both that shift plus the successful evacuation of the Super Dome. It was one thing to try to remove someone from an area that wasn't flooded who had some supplies and stick them in the squalor of the Super Dome/Convention Center, especially when you had people begging for help in getting rescued. Now it's time to get everyone out.