Spoilers - do they really spoil your enjoyment?

One of the things I've noticed in the hysteria surrounding the announcement of the publication date of Book 7 (which I still can't quite remember is called Harry Potter and the Deathly Hallows) is a number of people who won't be able to read the book the instant it comes out talking about how they'll 'protect themselves' from finding out what happens.

Now I'm the kind of person who likes to know what's going to happen.  I often read the last chapter of a book first so I can see what the big events will be (some books are harder to do this with than others!).  Especially in mystery or detective fiction I like to know the solution so I can enjoy reading the book, taking my time over the prose, without scrabbling through just to see who dunnit.  I didn't read HBP until it had been out for a couple of months and I already knew Dumbledore died (though not that Snape killed him).  It didn't spoil my enjoyment of the book in the slightest.

I fully expect not to read DH the moment it comes out.  I'm too mean to pay hardback prices, so I'll either borrow from a friend or wait for the paperback or a remaindered copy or something.  But I'll be happy to know from other sources how it all turns out.

So here's my question, does knowing the ending necessarily spoil one's enjoyment of a story?  Not according to however many million people watched and enjoyed Titanic, for instance.  Or for anyone who's ever re-read a book, or gone to see a film of a book or a real-life story that they already know.  It seems to me that the enjoyment is in the telling of the story, not so much the story itself.  A good story can stand to be retold any number of times.  Can't it?

ETA:  I made a poll!  *is very excited at mastery of LJ technology*.  Please tick the boxes and leave me a comment to let me know what you think.

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