Peter Wayner worries that piracy will destroy authors' earnings:
The kind of book I write, thick with equations that play to computer lovers, is also the first to be pirated. It’s a canary. O’Reilly Publishers, one of the top technical presses, reported that in 2008, the computer book market was the only segment to lose sales. According to the company, the category sold 8% fewer titles in 2008 than 2007.
I’m not going to write more books if the revenues will be wiped out by pirates. While authors like Cory Doctorow like to argue that the author’s real enemy is obscurity, there was no real uptick in the sales of my book when these pirated versions appeared.
Alan Jacobs agrees about the threat:
It's kind of an individual thing right now as Stephen King says about the book pirates, "most of them live in basements floored with carpeting remnants, living on Funions and discount beer" but if textbooks go digital then such bootlegging will become a full-fledged industry. Somebody will make money off it, but it won't be the textbook publishers.