My answer to this poll is 'did the author call it fanfiction?' It is imperfect-- death of the author, weird legal issues and all-- but that is, honestly, the rule I think should be in place for the AO3. As a tag wrangler, what we've been told to do above all is respect the author's wishes, and I feel 'this is fanfic' is the same category. If you consider it fanwork, then yes, please put it on the AO3.

And related to this-- and something I em>have seen cropping up-- is that there is still no archiving available for fanvidders and fanartists, and as far as I'm concerned that should be the top priority over debating whether or not fully original works in any medium are allowed. For me, that's the real crux of the matter.