Great posts, Lucas and Victor. Couple minor comments on comments above…

1) CC0 means attribution is not legally required. It doesn’t mean attribution is automatically lost or that releasing under CC0 is the equivalent of publishing anonymously. I expect lots of people will use CC0 and publish recommended but not mandated attribution/credit/citation info (the geeky word for this is apparently “norms”). Whether you want to legally require attribution depends on how much being able to legally demand credit is worth to you in creating more friction around uses of your work.

2) I don’t like the line that “PD is an American construct”. There are some important ways PD is more clear and more present in the US than most other places, but PD is an important concept that should grow everywhere. Some info at http://commons.wikimedia.org/wiki/Commons:Licensing#Material_in_the_public_domain and there’s a network explicitly for exploring the (very broadly defined) digital public domain from an EU perspective, see http://www.communia-project.eu/ … also it is a bit of a hack but I think the very broad conception of the public domain that I think is described in James Boyle’s book of the same name, as the inverse of copyright restrictions — eg fair use and other limitations, as well as voluntary commons, all expand “the public domain” of stuff and uses people can do without restriction as opposed to works that are wholly in the public domain, is a useful construct to at least think about.