This post is in response to
jessicaqueen's
entry complaining about authors who oppose fanfiction.
In general, I agree that authors shouldn't prohibit fanworks. I feel like I would be incredibly honored and thrilled if I published something and people loved it enough to write fanfic about it. I'd probably turn evil and start reveling maniacally whenever I encountered a heated shipper war.
That said, I think there are other reasons why an author would be leery of fanfiction besides a worry that some one else will write his or her own world better.
For one thing, they might be viscerally disturbed at the idea of people writing really OOC kinky smut about their characters... which, yeah, you could argue that they should get over it or pretend it doesn't exist or whatever, but for some authors these characters are their lives, and that's got to be hard to do.
More seriously, I think there's an honest worry about about legal issues, despite the disclaimers that most fic writers post. As you pointed out in your post, some fanfic writers really need to get over themselves... I know I've read writers that honestly convince themselves that even slight similarities between their fics and a new episode/book/whatever can only be the result of the writers going online and stealing their ideas. It's ridiculous, and I imagine very rare, but I have heard of it escalating. (Apparently, a couple of decades ago Marion Zimmer Bradley had to scrap an entire book that she'd written because a fan had written something similar and threatened to sue if she didn't get co-authorship and half the profits). Apparently, there's also some issue with copyright? Like, if somebody in charge decides that you haven't defended your copyright, you've abandoned it?
I don't know. I'm getting most of this from
George R. R. Martin's LJ. He's well-known for disliking fanfiction, and though I don't necessarily agree with his attitude as a whole, I think he's got some points that avid fanfic-fans like to dismiss as a defense mechanism. (I'm actually really curious whether he still tries to prohibit fanfiction now that his books are an HBO series. I've started seeing GoT-fic for the first time, so I'm guessing he's either loosened up or lost control.)
Tldr; I love fanfiction, and I love it when authors or showrunners or whoever promote it, but authors who prohibit fanfiction are not necessarily insecure about their talent. They might just be risk-averse or hugely attached to their characters.
(Also, in response to the second part of the post, fic authors plagiarizing other fanfiction verbatim is the most idiotic, ridiculous thing ever. There's absolutely nothing to gain, and a whole lot to lose. That said, considering the way fandom works, the idea that no one will ever have the same interpretation or idea as you did is equally ridiculous.)