Michael Geist has made a terrific film Why Copyright? Canadian Voices on Copyright Law giving the perspective of a who's who of creators, public officials, business folks (including the CEO of Skylink which got sued under the DMCA by Chamberlain for making interoperable garage door openers), archivists, librarians, academics and others on the need for balance in copyright laws.
Recommended. Many of the contributors refer to the importance of the public domain and if you really want to get a handle on the concept of the public domain then James Boyle's just published new book, The Public Domain, is bound to become the standard text.
Update: Prof. Geist made the film with Daniel Albahary, a law student at Ottawa and Michigan State universities. The film is available in several formats at http://www.copyrightvoices.ca.
Streamed versions are online elsewhere:
A full version at Blip.tv
An annotated version at YouTube
A version for sub-titling at Dot-Sub
In addition, the full DVD can be downloaded using BitTorrent. It's at
<http://www.mininova.org/tor/2054674> or via Vuze at http://www.vuze.com/details/2OQKU47Y56JSCE6RXQ2W5JNDSL3KBEM7.html