Current thought stream
If it weren't for fan-fiction, we wouldn't have things like Robin Hood, the King Arthur stories, the Iliad, the Odyssey and (sorry, folks) most of the Bible. We also wouldn't have writers of new fiction, because most authors start out by writing stories about real or fictional characters whom they already know and love.
It is for these reasons that I think that fan-fiction should be specifically legal and protected speech, though I don't think that people should be allowed to take money for unlicensed fan work created around pieces that are still under copyright.
Oh, and here's a titbit for those who hold that fan works harm copyright holders. Were it not for fan-fiction, I would not have purchased the Patrick O'Brian books. In hardcover.
Back to writing, now.