Part of what you're saying is the reason I have considered giving up the blog entirely - the meta, the diary, all of this takes away from the 'creative pool' from which I draw. It must, because there's a definite slowing of production since my involvement in these things.
On the other hand - you cannot find beta readers without networking. I have had feedback, struck up conversations, gained a brainstorming helper, then lost them to RL several times. It's why the majority of what I've written was not beta read, why I've mostly despaired of finding any help at all -- finding the right people online is a total crapshoot. I answered a request for beta and was the only one of 15 people the person emailed to even reply to her email. Times are tough.
Who says you cant write a story about a pairing you dont like? I think it could be written from a different angle than someone who is writing it as their One True Pairing. Which is a Good Thing.
I do not post publicly anything unfinished. Maybe that's a holdover from professional work, but it's both an odd paranoia and also a strong resistance to anyone seeing a piece beyond a handful of readers and my editor until it's ready to be "published." That, too, is a function of my previous experience, I'm sure.
I've felt no particular draw to write "Smallville" (for a variety of reasons) even though I know several of the authors, but if I did, I'm not sure I'd be put off by the fact I'm coming in "late." I suppose it's because if I did decide to write in it, I'd be doing so because I had a story to tell, and that would be independent of other opinion. Again, that may have something to do with my own peculiarities as a writer.
Anyway, what I've found the blog/LJ phenomenon doing is no so much prejudicing my ideas of a story, but my ideas of the writer . As is always the case, I may enjoy the stories of a particular person without actually LIKING the person in question much. And I've found through blogs that people I like are not always people who write stories I want to read. I may, BECAUSE I like them, try their stories after all. But the reverse is unfortunately true as well. There are some folks who I've discovered, after reading their blogs, I don't really think much of, and it does somewhat sour my inclination to read their stories, even if I had read them previously.