Today's Wall Street Journal (sorry, behind a firewall) has a great piece about Wall Mart's ability to recover after a natural disaster. There are clear chains of command; distributed support personnel and fleets of trucks to move goods where they're needed most. More importantly, the article notes the stores (in Katrina's case) were ready to spring into action early, when the storm was still over Florida. That seems to be the company's MO, too.
The speed at which Wall Mart recovered its own operations and was able to assist the hard-hit communities in which it operates has won it almost universal praise. First responders on the ground looked to Wall Mart before FEMA. It's likely they'll never look to FEMA again, either, after this episode.
Which just goes to show that in PR, actions frequently speak much louder than words.