On all of the O'Reilly titles DRM has been dropped, and Tim O'Reilly (TO) isn't at all bothered about the concern of piracy. He makes the point "And let’s say that if by putting DRM in it I sell 10,000 copies and I make my money, and if by having no DRM 100,000 copies go into circulation and I still sell 10,000 copies. Which of those is the better outcome?"
He also makes the generous comment "We’re delighted when people who can’t afford our books don’t pay us for them, if they go out and do something useful with that information." What a delightfully different attitude to those publishers who sit scrooge like on their little piles of books, miserly counting down loans like some latter day Ebenezer until they can reach out their bony fingers and snatch them back. Yes, it's an over the top piece of hyperbole I'll admit, but I think it's still a fairly accurate illustration.
TO goes on to make the point that free content increases visibility and awareness. Important is the need to establish social norms around payment, by honoring people, respecting them, and in return people will pay for products because they know that if they don't get paid authors can't do what they do. If 10,000 people are willing to pirate a book there's a very large number who are willing to pay for it.
This seems to be a much more sensible, adult and realistic approach to the whole notion of eBooks and DRM.