[sgath92]

> Do you think this actually hurts sales though?

It might in some situations. With music for example, some bands have successfully encouraged people to buy their releases by including "rare" tracks that, if they were released previously, were done so on obscure titles that even collectors have a hard time finding. If everything an artist creates is easy to find online through piracy, there's no trove of "rare" material unless it's stuff that's never been released (like practice sessions or stuff that didn't make the cut for previous releases, much of this stuff is simply subpar and doesn't encourage purchases much).

Its hard though to carry that idea over to books though. What would be the extra material, unabridged versions? Not many books have abridged/unabridged versions to choose from.

I guess the closest parallel would be books people buy because they have to, not because they want to. By that I mean things like textbooks where, if they were available easily on pirated sites, everyone would just download. I kind of think publishers know this, and that's why so many now carry a one-time use only keycode to unlock online content. If you have to retake the class you can't access the online content again without repurchasing, even if the book itself has not changed.