Okay, so here's the thing. I've got this sort of love/hate thing going on with fanfic. Always have. I've mentioned on my blog posts before that overall I'm not a huge fan of it from a professional writer perspective. (And I'm not going to go into the legalities or where the line should be drawn, though there's a nice run down of the various types of fanfic vs plagiarism here.)
But there's a few different sides to this, and there's nothing that gets people angrier faster than to be told that their work is not worth anything or is a waste of time - and that is a viewpoint that many published authors take.
I think the main thing to separate from it is why YOU write fanfic. Is it for fun and fandom? (which is a very common reason) Is it to gain writing skills? Are you hoping to become professionally published? Just writing as a hobby? Trying to fill in gaps left by the original author? Spinning off an existing story?
So let's get into some of the pros/cons/grey points, shall we? (And note, I do NOT agree with all of the points listed below, just that these are some of the more common arguments I've seen.)
One: It gives new writers practice and confidence. They get to play in someone else's sandbox where the world building is set up and the characters are known entities. This allows writers to focus on the craft of writing without worrying about the harder details.
While the above argument is true, at some point a writer has to throw off those training wheels. Because here's the thing, yes, writing in a pre-made world makes things easier, but it can also foster some bad habits and possibly limit the development of your own world-building. Also? I do read fanfic sometimes and what gets me is that often heaps of praise are tossed upon a particular writer or a particular story and when I go to read the story...I'm sometimes disappointed. Grammar can be an issue, but often the plots are sub-par or the characterizations feel wrong.
And then it becomes rather obvious that the only reason this story is so popular is because it involves a favorite pairing. Rabid fans will line up to gush over the fact that character x and character y are barebacking in the stairwell, even though in actual canon, said characters are mortal enemies. But even beyond the character twisting, I think it can give a budding author a false sense of security. They get a taste of what it's like to have their work loved...by a fandom that already loves and knows those characters. And who love ANYTHING written about those characters.
I've seen plenty of people on tumblr and elsewhere complaining about how hard it is to write fanfiction x and get hundreds of notes...and then they write something original and nobody cares. Or that they go to a con and whereas a fanARTIST might be in high demand, no one really cares about the fanfiction writers.
The other thing is that if you are trying to get published - whether that's books or comics or whatever, an agent or an editor is going to want to see original work (the 50 Shades fluke notwithstanding). I will NOT be able to hand in my Harry Potter fanfic to an agent and get representation, no matter how good the writing is. (And for a really good look at some thoughts on the comic book world, go check out Gail Simone's blog post on the subject.)
Two: But Classic Novel X was fanfic! Neil Gaiman writes Dr. Who fanfic! etc. etc.
While we've discussed a little bit this week about some of the grey area and legalities of fanfic - i.e. does rewriting a fairy tale count? for example, and I fully believe Neil Gaiman could write anything he damn well wants (And Neil was paid to write that ep of Dr. Who. He didn't just come up with a character called Dr. Blue who flies around in the RETARDIS, for the sake of comparison.), the fact of the matter is that yes, there ARE professional fanfic writers. For Star Trek, or Star Wars or Dr. Who or whatever. But those are LICENSED by the IP owner or the publisher. It's not the same thing at all. If there's a Star Wars anthology coming out, there will be a call for submissions. There will be a contract, etc. It might be a great opportunity for a fanfic writer to get some publishing cred.
The same is true for comics - although Marvel and DC are notorious for rebooting comic stories and developing alternate universes, it's still canon. It's still licensed
Three: It fulfills a need within a fandom.
Clearly it does, or there wouldn't be so much of it. Obviously tastes vary, and fanfic can be a good way to encourage a fandom to exist long past it's expiration date. (Particularly in the case of TV shows or movies or games, etc.) I have read some amazing writers (some of whom I have reached out to encourage them to write original material because they've clearly got a gift). I've also read some excellent stories - but again, some would never stand on their own without the foundation within the fandom. If it weren't for the fact that the readers already know those characters or worlds, some of it wouldn't fly. And hell, sometimes that's okay. Ridiculous fanfics can be fun as well (also known as "Crackfics" sometimes. And then you've got slash pairings, or AUs (alternate universe fanfic), cross-over fanfic, etc. etc.)
Entire communities spin off of fanfic fandoms - whether that's at fanfiction.net or An Archive of Our Own...or even the myriad kink memes I've seen on Live Journal. (Like this one for Dragon Age - people request scenario prompts- sweet ones, kinky ones, completely messed up ones...and writers or artists can attempt to fill them. The beauty of it is that it's all done anonymously. I may or may not have filled a couple of them.)
On a personal note, yes. I have written fanfic. Not much and I'm rather picky about it. I've got some rather hypocritical notions about it - 1) I would never write or read fanfic based on the writings of another author. I don't care how well it's written. It does bug the shit out of me. Obviously not every author is bothered by it. Some encourage it. Some ignore it. Some indicate it's completely out of line and won't be tolerated. For me, the biggest peeve is that it's not canon. I can love a book or a series to death and want more from the characters or a storyline, but writing something with characters that aren't mine feels like wish fulfillment It didn't actually happen and not trusting the author to tell their story as they see fit feels disrespectful.
2) Hypocrisy city coming up....I don't have as much issue with fanfic about TV or games, but it really does depend on the situation. Hell, you could technically call True Blood fanfic because it's so far removed from the Sookie books that they don't really bear much resemblance at this point, except for character names. It could be that I'm just not as tied into TV so I don't really care as much.
3) Which leaves me into game fanfiction. I write it. I read it. (Mostly shorts because I don't have much time.) So why the double-standard? I don't know. I think with some of the RPGs in particular, you're playing a character and in some ways it becomes a choose-your-own-adventure. Depending on the choices you make, the outcome of the game can be affected. So right there, everyone's play-through is a little different. People will write ficlets that fill in the gaps (for example Dragon Age 2 is told in 3 acts...but they jump ahead 2 or 3 years between each act and the game writers/developers don't really tell you what happens during that time. So it makes sense to me that people might want to attempt to fill in some of that, simply to make their play-throughs that much more involved. On the other hand? I've also seen stories that were upward of 200k words. Which boggles my mind - a) the effort involved is crazy amazing, but b) I think many published authors look at that and say if you can write that much, you should be writing your own novels...because at the end of the story you have something that you can't sell and can only be enjoyed within that particular fandom. When that fandom dies, what's left?
(Which is where people tend to jump in and say they only write for fun so it doesn't matter. Which is fine. Speaking as a professional with very little time left in my day, I can't remotely see "wasting" my time on something I can't sell or that doesn't enhance my career. It doesn't mean fanfic is right or wrong, just that the lenses some of us look through can change the view. There's a massive difference between writing for fun and writing for a deadline.)
So there we go. That being said, I also have less issue with fanfic based on tv or games or movies because no-one is going to confuse these stories as actually being part of the canon universe. A short story in a book universe? Maybe not so much.
In either case, the last point I want to bring up is respect. As noted above, many fanfic writers don't feel like they get any legitimate respect for their time and effort. And part of that may be because not everyone understands it or is interested in it or they feel it's illegal or whatever. That's one of the caveats of writing it.
But at the end of the day if it makes you happy, then that's all that really matters.
(All the picture quotes used in this post came from wtffanfiction.tumblr.com - these are quotes taken from actual fanfics posted around the web - clearly from the more pornographic/crackfic sorts.)