Thought this was interesting:
Abusing the People of Westeros
You probably know that I'm not a big fan of fan fiction. (I've written about it here and here and here.) If you go to the page linked to above, you can read what various authors think of fan fiction.
George R.R. Martin's argument makes a lot of sense; he created the characters and in the hands of others, they may do things that he absolutely never intended for them to do, act in ways that completely contradict what the characters are about.
J.K. Rowling is kidding herself if she thinks all the Harry Potter fanfic producers out there will keep it PG-rated. I don't even pay much attention to fan fiction and I know that there are a ton of X-rated stories out there.
Seems most authors are against it, to one degree or another. (At least the ones profiled here, most of whom are in the sci-fi/fantasy camp. If you read the comments, at least one of them argues that the author of this piece hand-picked fanfic haters to profile.)