I had a crazy friend who ate for years out of Trader Joe's
garbage cans. One day a cops were called. After, that
he still went back, but a lock was put on the garbage.
If you think it's crazy, I'm gonna guess your broke college-kid days (if you had them) are long behind you. :)
It's true that there have been cases where someone is successfully sued in this manner; the source of the danger (which could be food or a uncovered hole in the ground that someone falls into) is known as an 'attractive nuisance', ie something dangerous that is also irresistible. However, that's usually only successful in cases where children or animals are drawn towards the attractive nuisance because they lack better judgment. It would be hard for an adult to persuade a jury that he couldn't anticipate the risks of eating food from a garbage can.
IANAL, didn't do a review of AN cases, TINLA.
In their own words: "[Freegans] embrace community, generosity, social concern, freedom, cooperation, and sharing in opposition to a society based on materialism, moral apathy, competition, conformity, and greed."