When asked by About.com what Buffy the Vampire Slayer fans should do now that the show is over, Joss Whedon, creator, replied, "write fan fiction."
Joss understands. He gets the fans. He knows that imitation is the sincerest form of flattery, that fan fiction can only benefit the creator. It keeps people interested. It keeps them thinking. If what you have created has sparked the imaginations of so many minds, then you must be doing something right. Why fuck with a good thing? Why would you complain about the fact that people are so enthralled by the world you have created, and its characters that they just can't get enough? 22 episodes a year just doesn't satisfy the cravings. So they get their fix elswhere.
Okay, so there is a lot of crap out there. PWOP (porn without plot), fluff, tripe stuff that gets read by those obsessive types who follow Charisma Carpenter to every bloody con in the Western Hemisphere. But every niche has its crazies. And they are harmless- well creatively speaking anyway.
There is also good fan fiction. This is the stuff that actually captures the essence of a show (or Movie or Book series) and brings it to life on the page. It's not about making the characters act out your stupid little fantasies. Good fanfic writers will keep their characters in line. You won't see Wesley Crusher rolling doobies for his classmates, or Doctor Who pinching some hot yellow alien chick's ass. A good fanfic writer will write dialogue that you can actualy imagine the characters saying. And if they are writing Buffy or Angel fanfic, it will be smart, witty and genuine. It's not a simple task.