http://www.cracked.com/personal-experiences-1922-5-realities-life-in-tent-city-homeless.html 

"We got a lot of food," says Heather, "but about 80 percent of it wasn't edible. ... Some stores would drop off rotting food just to get the tax breaks." Or, as another source, Leslee, says, "People would clean out their refrigerators and bring us whatever was bad."