I have a hard time stringing together complete sentences when I speak because my brain is already six incomplete conversations ahead. If you want to play "guess that story" with me, you have to be a Level 12 Champion of Mental Hopscotch ... or just drink a lot of scotch. That's helpful in most interactions with me.
Why don't I really care about sharing ideas? Less than .02% will actually end up a as complete novel. There may be a horde of Chapter Ones running amok, but 100k novels are far fewer.
Guys, guys, guys, I love brainstorming. It's like crack for the imagination. I love throwing out what-ifs and then-whats. The best part of writing fiction is that -- in the idea stage -- there is nothing too absurd. Cyborg werewolves nesting inside the unfinished pyramids at Giza? YAY! What if those weres are hunting the bucktoothed pharaoh to stop him from dredging the Nile and angering the Nyads from planet Zork? What if one of the weres is a Mr. Darcy-esq sort of dude? Do cravats last around mechanical necks or does they start all pristine and white then in like, an hour, devolve into utter shreds? Does he use the tatters as floss after a kill? What if one of those tatters ends up being the Shroud of Turin?
The most useful thing about slinging ideas is that it pushes me to be twice as creative when I actually jot down the meaty bits of the main plot. Now, do I discuss a book as I'm writing it? Sometimes it'd be nice to, but then I'd have to explain the characters and where they're going and what's already happened and why... and I've already mentioned my inability to verbally complete a thought, right? Right.
Do I feel talking about a story before I write it makes it lose its creative lure? Nah. Do I find it helpful? Sometimes. Do I find it fun? Depending on who's playing hopscotch with me... you betcha.
If you were to discuss a book before you wrote it, what sort of qualities would you want in the people with whom you're speaking? Best-Selling Authors? Wackadoodles? Marketing Gurus? Sociopaths? Five Year Olds? Whiskey-Soaked Curmudgeons? Go on, share your ideal brainstorming party participants.