A number of years ago, when Hurricane Andrew(?) went through Fla., The news showed a number of people who had taken up firearms to protect their neighborhood. Painted messages on garage doors, walls, etc. said in BIG PLAIN LETTER...YOU LOOT WE SHOOT. I have not heard of anything like this since or even now.
Good news is, looting isn't very common, since all the people who would be looting your stuff are also stuck in a disaster area and are also barely surviving.
Seems like more of a problem for the people who leave town and don't return for a few weeks.