Giorgos Cheliotis, Warren Chik, Ankit Guglani, and Giri Kumar Tayi have self-archived "Taking Stock of the Creative Commons Experiment: Monitoring the Use of Creative Commons Licenses and Evaluating Its Implications for the Future of Creative Commons and for Copyright Law" in SSRN.
Here's an excerpt:
We provide data demonstrating the popularity of CC, examine which specific license types within the CC framework are most popular, and then identify contributing factors for the relative popularity of some of the license types. This includes individual author incentives, the consistency and aims of the online communities which adopt CC as a licensing model, the underlying medium (text, photography, audio, video or interactive
content), the intended use of the work, as well as the sociopolitical, legal and economic background of the jurisdictions where the works are being produced. We show that the spread of the licenses is global and encompasses both developed and developing nations with varied cultural and historical backgrounds, which we claim is indicative of a general social shift towards more open collaboration and the rise of a new global consciousness of sharing and participation across national borders. . . . In conclusion we examine to what extent copyright law and policy should be informed by the needs and choices of this new generation of authors adopting CC licenses, also taking into consideration the changing interests of society in the digital age.