After some reflection, (maybe not all that much though), I would think that transfer into a world must be tied to trusted creators. So objects must be linked to a certified, perhaps bonded even, creator, who will defend/warranty the authenticity of that object and pay penalites etc if they are not really theirs.

This scheme obviously could also include the owners as well–but it would be more complex I think to track it all down. The Creators are at a slightly higher vantage and could have 3rd party certificates etc.

Given the ebay/vuiton case, it would seem that this is sorta where even the web may be headed.