Anne Arendt and Dustin Fife have published "Impact of Public Domain Resources On Public Libraries in the United States" in the Journal of Librarianship and Information Science.
Here's an excerpt:
Ownership and rights issues relating to electronic resources can be a source of angst, confusion and litigation. This is due in part to the automatic copyright many individuals receive, including in the United States, upon creation of an original work. However, there are options available for relaxing these rights. One of these options is Creative Commons Zero. . . . Based on the above, this document researches the awareness, complexity and effects of Creative Commons Zero and related licenses on libraries as perceived by library directors and managers across the United States. In order to accomplish this, a quantitative survey was administered in an anonymous web-based format.