Let me offer myself as a case in point. I travel to San Francisco once or twice a year, and every single time I visit, I resolve someday to move there. I think my resolve has been substantially weakened in the past several days. Having seen how ineffective disaster relief can be, I am suddenly disinclined to live someplace where I might need to rely on it. And that's a good thing. The horror being visited on New Orleans today has made it less likely that I (and others like me) will be victims of an equivalent horror in the future. Had the relief efforts been more comprehensive, I might still be a future earthquake victim.
So those are two reasons we might want to rethink the policy of giving federal assistance to disaster victims. It encourages people to live in dangerous places, and it denies people the opportunity to accept higher risks in exchange for lower housing costs. Those abstract principles might be partly offset by any number of real world considerations. But if we want to build a better world, no truth should be ignored.