Sorry to double post, but I just had to mention this before I forget:
"The Organization for Transformative Works (OTW) is a nonprofit organization established by fans to serve the interests of fans by providing access to and preserving the history of fanworks and fan culture in its myriad forms."
A fantastic 147-comment discussion is going on at John Scalzi’s blog about the issue, and he raises some great points. The best of which is that fan fiction largely operates on a don’t ask, don’t tell policy, and by organizing and uniting to fight a legal battle on their rights, it’s likely to cause publishers/studios to lend their considerable legal weight to the battle, and fan fiction writers would be more threatened than they are now.
They also debate when the line of "transformative" begins.
My thoughts on the matter are largely undecided. I have a couple worlds that, if fan fiction were to be created, I’d be a little hurt. I feel awful protective of my worlds.
On the other hand, anything with the word "fan" in it isn’t all that bad (maybe stalker fan ...). And it is a compliment to love someone’s world so much, love someone’s characters so much, that they live on in your head and you have to write their stories.
I see good points on both sides, and I would definitely prefer the don’t ask, don’t tell approach. Organizing and making fan fiction legal starts making me uncomfortable.
The thought that all this could lead to other people making money off my worlds? As Lula in the Stephanie Plum series would say, "Nuh-uh."