I think the big problem here is how to determine what is abandoned and what is not.

I know I'd be very upset if I went out to try to find my wife or a family member only to come home and find my place robbed of MY SUPPLIES because I had the foresight to have some extra food.

OR, even worse, what if you thought it was abandoned because you couldn't see anyone, or no one answered the door but I was out back getting some fruit or veggies from the garden... I walk back in my back door to find you rummaging through my cabinets.... that wouldn't end well.

Trust me, I know many people think they can just take what they need but that will get you in even more trouble than you are in.

Obviously if you are STARVING TO DEATH you are gonna do what you gotta do but that doesn't normally occur during a "Katrina" like event.. you get hungry, you may not eat for a few days but you are not going to go 3 weeks w/out food and starve to death.