Rowling and the folks have taken advantage of the loyal fan following of Harry and friends. They take into account that at least 90% of the movie goers have thoroughly read the books and therefore leave entire chapters and characters out of all the movies, moreso in this crucial turning point than anything. The beautiful thing about JK's works was that she took seemingly insignificant details in previous volumes and turned them into major plot points in the end. And this has been gravely overlooked by the WB and movie peeps. The movie was like swiss cheese, tasty, but had a few holes.