Birds need to fly from tree to tree. Monarch butterflies need to migrate to a Mexican mountainside. Caribou must hoof it south or north, depending on the season. And TV-show DVDs need to be free.
That's what I've learned. I sent my son some cool SF shows (Battlestar), and after watching them he sent them back. I watched some other (PBS) shows, and sent them on to him. I got some other shows - Boomtown, etc. - from on my last visit with him, and I'll be sending them back.
People generally aren't going to want to watch a TV show a second time. But ... you can pass them on, giving other people some fun entertainment, too. Every DVD starts out with stern "FBI" warnings about how copying DVDs is illegal and buying them is wrong, subject to a $250,000 fine or a million years in jail, not to mention waterboarding.
But how about re-gifting? DVDs want to say, hi, glad to find a new friend! When I send back these latest DVD, I expect my son to open a window, cradle a TV DVD in his hands, aim it toward a deserving friend, and let it fly.