Ok so remember the article I posted from http://3ders.org about the robotic telescope with 3d printed parts? Well I was going through the site this morning and came across this video on their blog site. What a great commercial for some of the benefits of 3d printing. If they threw in there, as @ThantiK mentioned in the past, building the printers too they would have a well rounded commercial.
http://www.youtube.com/watch?v=3HSE5vp2ulU
One of my favorite parts of the video is the printers screwing up the prints, but the narrator is telling you to keep trying and learn from your mistakes.