And if they start going after people who strip DRM for their own use, then the publishers will start losing people who will stop buying ebooks and either return to the public library system or start using the second-hand market.
I've got thousands and thousands of books that I've bought over the years; I don't need to buy another book to keep me in reading material. I wonder how many publishers will come and go in the time it would take me to re-read all of them?