I don't think there are any rules, really -- there's just inconsistent fandom conventions. And then people give you shit when you "break" a rule you mever even knew existed. :-P

I'm not a fan of warnings on fic, either. If it's part of the story, then I'd rather find out about it as the characters do. Knowing that someone is going to die is worse than being surprised, for me. I know other people feel differenty, though!

So now I'm wondering: If you write a fic set after OOTP, do people really expect you to warn that Sirius is dead? And ditto for Dumbledore post-HBP?