Actually if you use software out there that takes the name you use on the credit card to buy the book and puts it on every single page of the PDF it has been proven to be a pretty good deterrent for the bit torrent problem.
I think it's a perfectly good deterrent for most people without adding on annoying DRM or anything else that actually impedes the reading experience.
(By the way, you do know that Apple silently embeds your name and email in every DRM-free music file you buy from iTunes, right?)
It might not be as intrusive as annoying DRM, but it still makes reading my ebooks frustrating.
If they wanted to watermark my info into the file to prevent file sharing, that's fine. Printed on every page? Obnoxious. It's another case of legitimate purchases having a disincentive that piracy doesn't. I bought the book, I know I bought the book, I don't need to be reminded 272 times in the process of consuming it.