Social Justice Henchman
WotC products were turning up on file-sharing sites within days of release long before they started offering PDFs. All it takes is for some enterprising scofflaw to cut the spine off the book, dump the resulting stack of loose pages into a duplexing, sheet-fed scanner, and find a way to kill time for about an hour. When it's done, they've got a full-colour PDF - it'll even be searchable if their scanner has decent OCR software. Yes, that kind of hardware doesn't grow on trees, but it only takes one person doing it once to make that book a permanent resident of your favourite file-sharing network.I'm not saying it's right, but the PDFs on the filesharing sites had to come from somewhere.
(Heck, the PDFs of the 4E core books you'll find on the filesharing networks aren't from RPGNow or DriveThru at all. Somebody at WotC leaked the digital masters - illicit copies were being distributed electronically before the books had even been printed.)