For whom the pen?

In reading another friend's livejournal this afternoon, I realized something specific about the way I write.
 
Some people write for themselves, for their own pleasure and/or vilification. They write because there is an inner demon struggling to get out. They write because they love the way their own words sound (and not necessarily in an arrogant fashion - it's a love of language). They write to feed the beast. I understand this. I even experience it from time to time, though not as often as one  might think. But I'll get back to this.
 
Some people write for other people. Nothing wrong with this, either, but if I try to write for someone else, I end up sounding forced or like a demented Hallmark card. Now this isn't to say that, as writers, we should ignore our impled audience. That's not what I mean at all. When I say people write for other people, I mean they write with the express purpose of getting the acclaim/attention/praise/censure of the other party and they tailor their writing for that specific purpose.
Needless to say, this can get rather complicated.
Many people write papers for their teacher/professor. By this I mean that they specifically tailor their language and argument for an A. They don't necessarily write what they really think, or write in their own style, but they mimic what they think their teacher/professor wants to read.
Personally, I find this to be a load of crap and my students suffer for it if it's too obvious. I assign them a paper to hear what they think, not to have them vomit my own words back to me.
This isn't always the case, of course. Sometimes writing for someone can produce original and even beautiful work. I just think that's the exception rather than the rule.
 
Now as to my personal theory.
I write - whether an academic paper, a story, or a poem - for the subject: for the work itself, for the subject(s) of/in the work, for what needs to be said rather than what I think someone else (even myself) might want it to say.
When I write, I try to allow the story/argument/characters/ideas to speak through my hands rather than forcing the words to articulate something external to the patterns of those ideas. As a result, I often go back over a page and am only able to recall writing about one quarter to one third of it. It's very much like what I imagine automatic writing to be. Only I'm not going to claim to be channeling some long-dead author (W.B. Yeats, are you listening?).
Regardless, I think the subject (story/character/idea/argument) of the writing should speak louder than the desires of the audience or the imposition of the author. Naturally, the author must choose the subject (at least to a certain extent), but he or she - I believe - should also not attempt to force a subject to go contrary to its nature.
I think this is probably a great source of frustration for many "failed" writers. They have this idea of where their work is going to go and they mean to make it go there, even when the work needs to go in an entirely different direction.