Keeping a secret
By now, the Harry Potter hype machine has told you all about the pre-shipped copies, the scanned book and the spoilers. No doubt it'll sell a few copies, and no doubt the reported $20 million on security (not to mention fedex expense) was both useful and ineffective.
The interesting thing for me is how the Net changes what it means for something to be a secret. Five hundred year old technology (books) is just too slow for the Net. The act of printing, storing and shipping millions of books takes too long for a secret to ever be in a book again.
My solution? A hybrid. Publish the first edition of the book without the last three chapters. Take your time, save the $20 million. Every purchaser then gets access (hey, everyone gets access) to the last three chapters on launch day.
Books are souvenirs. No one is going to read Potter online, even if it's free. Holding and owning the book, remembering when and how you got it... that's what you're paying for. Books are great at holding memories. They're lousy at keeping secrets.