I found Possessed, a short documentary on hoarders, fascinating because I teeter on the brink of hoarding myself and have to fight it. Some days I am more successful than others. Notice how coherently the subjects talk about their obsession. They know it's pathological, but they can't stop themselves.
I was able to beat my hoarding of cardboard boxes ("Hey, it'd be a waste to toss these cardboard boxes into the recycle bin; I could re-use it someday, like maybe if I have to mail a package or something") when a friend of mine was moving and needed cardboard boxes to pack up his things. I gladly handed over my stash of cardboard boxes, with the instructions that when he was finished, the cardboard boxes were his problem. That solved two problems. I was able to get rid of my cardboard boxes with a clear conscience, and my friend got a bunch of moving boxes.