NSK-
(my personal favorite, the public domain, has relatively little support).
I am very interested in learning more about your reasoning on public domain and why it's your favourite. If you have enough time, please give me some reasons why a site admin should allow wikiauthors to choose public domain for their contributions. If you wanted to make me support PD, what would you tell me?
Two reasons: 1) It's compatible with everything. Never, ever worry about this crap again. Ask yourself if you realistically want to go after "infringers".
2) Copyleft requires enforcement, i.e. coercion. I believe this sends the wrong message, is a bad long-term strategy, and does not reflect well on our movement. As an opponent of copyright law, I also don't want to give people the argument that copyleft needs copyright to work.
That said, the differences are often exaggerated, so I don't lead personal crusades about the issue.
If you want a detailed discussion, you should talk to Jamesday on irc.freenode.net.
Regards,
Erik