when I mention one of my books (making clear that I am the author) in an Amazon thread asking specifically for books with that theme, and people neg me (vote my post down as not contributing to the discussion). There is a difference between spamming threads with a book ("you're looking for vampire romance? Read my colonial Virginia historical!") and mentioning it where it's appropriate. And it was entirely appropriate for the thread.
But hey, it's Amazon. Most readers are okay with reasonable promo, but a few folks there are deeply opposed to any sort of author promotion. I figure that as long as most readers don't mind my promotion, I'm doing well. An author just has to take her negs and keep on plugging away:-).