DRM will always be a thorny issue. If you buy a paperback (usually for a similar price) you can do what you want with it, you can give it away, lend it or sell it. With an ebook you can't do any of these things. I can't even put one of my books on my partner's e-reader.
I've always wondered what authors think of e-books. They might get more sales, but I discovered many of the authors I like through second hand and borrowed books.
Today's DRM implementations do allow for multiple devices to be authorized to the same account. So for example, if I had two Sony Readers, they could both be authorized to the same account and the DRMed ePub could be shared. Given this, it does make it possible to share the same eBooks with your partner. I do share some eBooks with family.