I know there is already a thread on sub-forums, but I wanted a poll, so...
I definitely feel that there should be a forum specifically so that Obsidian can spoil the game as completely as possible as soon as possible (including plot & story details). I'm also quite certain that there are a large number of people that wouldn't have any interest at all in reading those spoilers, so a separate forum seems the logical solution to me. Speaking for myself, spoilers don't bother me very much when playing a game, and it isn't uncommon for me to use a walk-through as a review of a game that I'm considering playing.
On the subject of special forums exclusive to the kickstarter contributors, I have very mixed feelings:
1) On the one hand, it filters out people that only have a casual interest in the game -- especially since these people are unlikely to actually have the money to purchase it when it comes out, either, since the purchase price will be higher than the KS price.
2) On the other hand, there is a high probability it will lead to threads being posted twice (or more, if there are several "exclusive" forums), making it difficult for interested parties to follow the entire discussion.
My opinion on this is a very soft "No, no special forums for KS contributors", but I'm willing to be convinced otherwise...