I'm far enough through the book now to have guessed who is going to die, so it's not a great shock. He has been in danger since the start of the book. He has that untrustworthy house-elf living with him, and it now seems like he is going to do something reckless to help Harry, but I would have still liked to have had it kept a secret until I actually read that chapter.
I don't mind it being written in this thread, I think people would have expected that, but why can't everyone use spoilers in their posts outside the forum for Book 5?
And the thread title in the Book 5 forum about the death, which appears daily if you do a 'new posts' search is a little obvious too. (The Sirius demise.....)
When I finish I'll post more, but did anyone else think it might be Arthur Weasly who was going to die when the snake bit him? I think that was deliberately done to fool anyone who didn't know yet. Hagrid being beaten-up by Grawps was also a misdirection to who it was going to be.
I was surprised that JKR gave away the fact that a major character would die, but not making it obvious who it is until the end, as she does, is very clever.