Update: Turns out that it's not a disagreement between Paizo and WotC after all. WotC has decided to stop selling PDFs on-line altogether, citing piracy concerns. They've also filed suit against 8 people for uploading the PHB2 onto peer-to-peer networks.
As I point out in the link below, this makes about as much sense as Rowling's famous piracy-driven refusal to authorize Harry Potter e-book sales.
http://www.teleread.org/2009/04/07/w...right-lawsuit/