Um, that sounds wrong.
Rape and other things that may be unpalatable to some in fanfiction. WAFF, deliberate OCC-ness, crack humor, character death. Some of us really need to know what we may be getting into because we are sensitive little creatures prone to reactions of high emotion--we get really scared, we get really angry, we get REALLY turned on and don't like being turned on.
Of course, the argument can be made that author's warning take all the surprises out a story. I mean, can you imagine a manga-ka telling you in a preamble of a chapter exactly who's going to die?
What do you think? I like to give thorough warnings to cover my bases, but I sometimes tend to lose it and blab too much in my descriptions and author's notes. I like to read long author's notes, though (they entertain me) but INTERESTINGLY, I don't want that many warnings even though I like to give them. The whole string of acronyms can just ruin a plot--oral, het, torture, sentimentality, hardcore boysex.