Why don't we use DRM on our e-books?
We make our books available in three different formats - paperback, Kindle (which you can buy from the Amazon store) and EPUB. (which you can buy right here on the site) For the two electronic formats, we don't use any kind of Digital Rights Management to "protect" our books. There's a variety of reasons why we think DRM is just a Bad Idea.
The first is that it implies I think my readers are untrustworthy, which is denigrating to them. Second, legitimately sharing the book often leads to increased buzz (see this study and this report). Third, it's solving the (perceived) problem at the wrong level, applying a technological answer to a social and legal question.
And fourth, it's a gamble against the wisdom of crowds, which is never a good bet to take - there's an awful lot of smart people out there on the Internet and it only takes one of those smart people, just one out of the many, to break the security and the whole enterprise is completely useless.
And once one person breaks the security, then circumvention will end up in the hands of everyone, and get easier and easier. (Remember unlocking iPhones?)
Now the bet against the wisdom of crowds has been conclusively lost, because one person has made it very easy indeed to circumvent the DRM on Kindle books, I feel even more that DRM presents nothing more than an annoyance to legitimate uses, but not very much of an annoyance to illegitimate ones!