Copyright Questions

Lawrence Lessig's blog http://www.lessig.org/blog/ might be a place to find a lawyer. Questions for a lawyer (and perhaps waiting for judges in real cases):

What is the current status of implied consent, and how might it apply in the case of wikis' normal operation of creating derivative works?

How much/what kind of edits make something *not* a derivative work, but a new work, with copyright held by the editor(s)? Do they then jointly hold the copyright?

What happens when signed work is edited (making a derived work), and the signature is then removed? What if the work is edited so much that it would no longer qualify as a derivative work?

What means (if any) are there by which rights are given *by default* from copyright holders to wiki administrators or other participants, beside implied consent, fair use and the Berne Convention's anonymous language that by default?

Who holds collection/compilation copyright when there are many compilers?

When does joint copyright exist, and how does it work? actually here's a doc on this: http://www.ipr-helpdesk.org/docs/docs.EN/JointOwnership.html