Ok, so I have this theory.
My theory is that many writers start out doing fanfic of some kind, whether they know that's what they're doing or not. They're intrigued by an idea, person, tv show, movie, or whatever, so they decide to write (or rewrite) a (part of the) story.
That's how I started. Well, I started with two things, one an "original" and one an "episode" of a TV show I plan to take to my grave. I think the "episode" came first, but I'm not sure. It was like 10 lines in a diary (the only diary I ever kept, and I wish I hadn't thrown it out in a fit of teenage mortification), but it was definitely the equivalent of fanfic.
We didn't call it fanfic then; in fact, I think many people thought they were the only ones (and certainly fanfic wasn't as common before the internet). I've been a fanfic snob in a lot of ways (I write original material!), but I certainly wouldn't grill it over an open flame, and I definitely wouldn't call it a scourge. It does seem to draw attention to the original material in question, along with fansites and fanlistings and the like--and most media has become interactive media, with writers and producers visiting fan sites to gauge how well ideas are working.
I got talked into trying my hand at fanfic a couple years ago, and I caved. And, horrors, I enjoyed writing it. (I didn't write much, but can I just tell you--it was good. I'm really proud of what I ended up with. I wrote it under a pen name, so it's out there, but as of right now, I'm not telling you where.) In fact, it worried me a little how much I liked doing it.
I didn't have to build my own characters and relationships from scratch; I didn't have to build a world complete with rules were believable. I didn't have to face that first blank page, wondering where the heck I was going and how I was going to get there. A whole backstory already existed, so it felt like diving into the middle rather than trying to figure out where the beginning of something new was, and how I was going to make it go anywhere.
One of my greatest fears has always been that there won't be a new story in me. I write novel-length material, and the number of short stories I've written can be counted on one hand. Some of them collapsed in on themselves and have been relegated to ruins that I might someday excavate, but don't want to right now. Short stories just aren't my thing. (Look at the length of anything I write, like my blog posts--I seem to have a defective "write short stuff" gene. *grin*)
When you write novel-length material, or maybe I should take a Gestalt-type responsibility here and say when I write things that long, I get attached to my characters, my worlds, and leaving them to go someplace completely different...that's hard. Recently, trying to go someplace new, I had a complete meltdown on the launchpad, the idea burning up into the equivalent of fried circuit boards and plastic. I haven't completely abandoned it yet, but I keep looking at that scorchmark, terrified that I shall never write another story. Believe me, the urge to write is still there, but a novel-length idea that's actually growing into something that will bear fruit is eluding me.
I know some people write fanfic when they're blocked with original material. What's hard for me is I feel like it's easy to fall into the relative comfort of writing in a world that has endless possibilities, because you can fiddle with canon, argue cannon, and Mary Sue yourself, either subtly or overtly. Mary Sue may be a real scourge, but she can be fun, even if she never meets anyone in your writing groups. She can be a dirty little secret. Or a confession that draws us closer to other writers. I think being Mary Sue can be what prompts people to start writing.
What do you think?
But writing fanfic that is convincing, compelling, and appealing to fellow fans is entirely different. I would argue that writing good fanfic is as challenging (or more so) than writing in any other genre.
Why?
Fanfic writing must somehow capture those elusive elements of a show that are common denominators for all fellow fans. If you think that "Joe" (for example) is a deranged psychopath, but the rest of your fandom loves him, you will have an uphill battle convincing anyone to read your story.
Extricating yourself from fanfic is also daunting. In an original story, you can *claim* that you are not a part of your character, and who is going to challenge you? But in fanfic, you have to be careful not to interject yourself into the story in a way that startles your readers. I didn't realize how susceptible I was to this phenomenon until I had written three fanfics from three different points of view, all with the main character struggling in school.
A final challenge to writing fanfic is that you are dealing with readers' minds that are already set. Original fiction allows you to reach each reader in a unique way. Writing fanfic forces you to create with exacting precision: you must bring something new to the table without upsetting the applecart.
That's an interesting point, about fanfic being challenging as or more challenging than original stuff. You do make a good point about how fans are pretty rabid about how they see their fandom characters.
In fact, I think it's an interesting reflection of the writer, how each person portrays the characters a little differently. I don't think there's any other place you can see how much our own experiences and beliefs affect our writing.