The EFF have a concrete example of why they believe the proposed WIPO braodcasting treaty is so important.
"The Smithsonian Institution recently announced a joint venture with Showtime that gives the cable TV network exclusive commercial access to the Smithsonian's archival materials (much of which consists of public domain materials)...
This arrangement is troubling for many reasons. In the words of Ken Burns, one of America's most accomplished documentarians, "It feels like the Smithsonian has essentially optioned America's attic to one company, and to have access to that attic, we would have to be signed off with, and perhaps co-opted by, that entity."
But consider just how much worse this arrangement might become if the WIPO Broadcasting Treaty comes into force. Under current copyright law, Showtime would have no exclusive rights over any public domain materials that they broadcast on their "Smithsonian on Demand" channel. So subsequent creators remain free to record the programs, extract the public domain elements, and re-use them, without fear of copyright lawsuits.
The Broadcasting Treaty could change all that. By creating new exclusive rights for broadcasters, the proposed treaty could block subsequent creators from recording and extracting the public domain material from the broadcast. Instead, they would have to independently obtain access to the original public domain materials. But Showtime has already locked up a deal that gives its people exclusive access to the originals. Catch-22!
It's bad enough when private parties lock up exclusive access rights to public domain materials in archives, museums, and libraries. Combine that with the Broadcasting Treaty, and you have a recipe for a public domain land grab."