Fascinating stuff. Thanks, Alrik <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
My general understanding is that the copyright holder can demand the removal of any and all unofficial stories/uses of their character(s) at any time - but that most do not bother with anything that is making no money for the creator or anyone else involved.
Published fan fiction is making money using other people's copyrights, so is obviously stopped ASAP.
Most professional writers I have ever seen an opinion from will never read fanfic to avoid any possibility of lawsuits, and most professional companies are the same.
Even if 99% of fans would say nothing in the event of similarity, there is always the 1% who head straight to the courts, and no publisher/author wants that.
It would be very hard for a writer to claim that they weren't even slightly influenced by a story they had read, after all, whether they were already working on a similar idea or not...