So get on it you filmmakers. Starting using interesting public domain footage in your movies doesn't forget the past where you came from! All that history is how we got here today. And all you entrepreneurs and business people never forget that this stuff can be repackaged and redistributed for next-to-nothing and you can even alter it and add your own copyright to your "new" product. It's a very lucrative business, one that multi-million dollar companies have been built on. Don't believe me? Consider law books. These are books that are public domain, and they are mandatory for everyone who works in many different fields like government and criminal justice. These books are purchased for many hundreds of dollars each. So...yeah! It can be done pretty easily. If you make an instructional video to accompany these books you put out, even working in some public domain video perhaps, you've got yourself an exceptional product that people want to buy, and it costs you absolutely nothing in copyright fees. Consider this from a strictly business point of view and you'll start to see what I mean.