My college-aged son has gone dumpster-diving tons of times. He would come home with a lot of baked goods and produce that had been thrown out. When someone caught him at it (rarely), he would say he was looking for boxes. Once a guy caught him red-handed with a 20-lb bag of potatoes. The guy glanced behind him to be sure no one was watching and then urged him, "Go ahead! Take them, quick! And take this other stuff, too!" Other places won't allow you to have free stuff, but if you drive by at different times, you might find a grocery cart next to the dumpster that "just happens" to have baked goods that are still fine. That way they can say they throw it out, but they keep it out of the actual dumpster for people.
And one of my favorite occasions was when we drove by a grocery store dumpster and an older, obviously very poor man was reaching in and had armfuls of bread. He saw us and stammered, "It's...it's for my dog!" I smiled and said, "Great, go for it!" and he looked so relieved that I wasn't going to call the cops on him.
Half our household furnishings have come from dumpsters. It's pathetic that stores throw away so much stuff, but hey, if they're dumb enough to do it, I'm smart enough to take advantage of it!