Movies and music stream very well already, unless you have full TV seasons that you want to give away, I don't think you'll get much traction there.

The one place that this could work well is games. If Steam had a setting that would automatically download and install demos for the hottest new games, I bet a lot of people would try them out. I haven't used it in the last few months, but I remember seeing demos available for that I would be happy to play if I could do it right then instead of having to download, install, and (half an hour later) finally play.