This blog posting on teleread has a nice discussion of Social DRM. I particularly like this quote:
"We could take e-books more seriously as a medium if we could truly buy them, especially for future use on new machines with different operating systems. Or present use on the cellphones, PDAs and other gizmos now proliferating in many households."
I think that's the real issue. As a consumer, I do not want to rent or subscribe to media, I want to own it. Period. I want to own it and use it any way I see fit—no matter whether it's on a Linux box, or a Mac notebook, or whatever. I think that's the key aspect to downloaded music files, and I think that's the key aspect to eBooks.
As the article mentions, the PDF eBooks we sell from the Pragmatic Bookshelf are not encumbered in any way with DRM. You're free to print sections off, have a backup copy, one on your laptop and hard drive at work, and so on. You're not free to share your PDF with others, that's all. Your name is encoded within the PDF, and also stamped on every page, so it really helps to keep honest people honest.
We're also trying to set an example, and I really hope this one sticks.