This change also applies to iBookstore sales. I'd add that getting more data is helpful, but the iBookstore needs to adapt to changes int the market. The reflowable (for iPhones) and fixed format (iPads) versions of ebooks need to sold from the same page, with buying one automatically meaning that the other is also owned. And authors/publishers should be able to upload both files, easily exported from InDesign, at the same time.
For textbooks, fixed-layout is marvelous, since it means an ebook's interior, page-breaks and all, can look identical to the much more expensive print edition. But students also need a reflowable version for other situations.