Fanfic vs. 'Original' Work
So sartorias was asking for topics for post-Bittercon discussions, and I brought up the question of what the differences (in motivation & content) were between fanfic and writing that isn't fanfic but is still responding to/in dialogue with prior works. One thing led to another, and here I am trying to write up a conversation-starter.

So you know where I'm coming from: I don't write fanfic any more. This isn't a value judgment, just a statement of fact. The last time I wrote/composed fanfic was when I was... six, I think? My parents still have notebooks which have me continuing the adventures of Jason January & the Space Cadets, as well as even older notebooks containing my great-aunt's transcription and illustrations of stories I dictated to her about generals of the Three Kingdoms period when I was very young. When I did write fanfic, it was motivated by the feeling that there wasn't enough of a particular kind of story - not enough stories in which Jason January foiled Hercules Canute, or in which Tsao Tsao was the hero instead of the much-maligned villain. This seems to be one motivation for writing fanfic. Others - perhaps more common - include the subversion & reinterpretation of the surface message or meanings of a text, 'correcting' perceived errors or failures on the part of the source text's creator(s), and personal gratification, aesthetic or otherwise. This list is probably far from complete.

The reasons I listed for why authors might write fanfic could also drive authors to compose 'original' works that respond to or are in dialogue with a pre-existing text, of course. (Most, if not all, of my fiction is driven by the twin desires to revisit or reinterpret works that I love or to subvert genre tropes that annoy me.) Essentially, my question is: Aside from legal, monetary, and hierarchy of taste issues (i.e. the perception that 'real fiction' > fanfic), why do writers choose to write some stories as fanfic as other stories as independent works? When and why is playing with someone else's toys more appealing than creating/copying your own, and when is the reverse true?

Inquiring Alecs would like to know.