Larry Lessig proposes a tiny tax on copyrights older than 50 years. This functions as a mechanism to sweep out old copyrights that no longer have any economic value for their holders. Read up. I think this is a good idea.
(Only read this if you’re a fellow copyright geek. This seems to violate the Berne convention‘s ban on formalities. They say since it’s outside the 50-year minimum we can do anything we want, and anyway that a tax is not a formality, but these don’t ring totally true for me. Admittedly, however, my knowledge of the Berne convention and its interpretation is limited. Hope it works.)