I can think of a few ways that
WotC could make the physical products (or official PDFs) more attractive.
One, since they are combining physical products with an online service, why not print books with a unique serial code that can then be used to get additional online services/goods.
For instance, what if each
DMG had a unique keycode to unlock the online Encounter Builder? What if each PHB had a unique code to unlock the Character Generator? What if each
MM had a unique code that would (gasp!) unlock monster tokens of (double-gasp!) free virtual minis for the Game Table?
By putting all these services behind a password protected User Account (
DDI),
WotC can tie the keycodes to that account. Any pirated or borrowed books would not allow those users to access that online service b/c the keycode will have already been activated by a
DDI subscriber.
Yes, people will still pirate the books, but there will be ADDED incentive NOT to.
The problem with this model is that it's hard to charge a customer TWICE for something: 1) for purchasing the book, 2) monthly subscription to use
DDI tools.
They could fix this by still requiring a registered
DDI account to activate the now "free" services that come with purchasing a book, but still having an "advanced"
DDI with extra features for a monthly fee.