Issue is not whether or not someone has copyright to their own creation--they do, The issue is about how to licence usage of digital goods which in fact SL does not and never intended to do.  Perms are not a good enough substitute for a licence between parties. Creators have the right to licence their work however they want--CC or limited use or whatever else--see the latest options on the CC site.  The point on registering/trust for a piece of digital content is to aid the seller in knowing that they are buying a legitimate item and not something that is identical but ripped.  I think most people want to do the right thing when they purchase a digital item and there needs to be more assurance that can do so.