I couldn't answer several of the questions, as I don't write in those areas. But for the tv and movie fic that I do write, yeah, what others have said about not really caring about the writers, but I'd really rather not know whether the actors read fic. I know actors who have read fic by friends of mine, and who have been fine with it, but that's still a line that I would rather not cross for gen, het, slash, whatever. I know the actor isn't the character, and most actors would (one would think) be good at keeping the two separate, but I am writing about physical characteristics and mannerisms that the actor portrays. I'd rather not take the chance of making them uncomfortable.

Merry also made a good point about not wanting fic to affect canon. Pleeeease no. It's disconcerting enough (and annoying, oftentimes) when the creators bend their vision to fandom in general; I don't want them reacting specifically to fic. No.