This actually pisses me off, a lot. I don't put my ebooks up on torrenting sites or distribute them - but seeing my own email address show up on every page of my ebook means that I'm not going to buy from you again, ever.
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?)
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.
It might not be as intrusive as annoying DRM, but it still makes reading my ebooks frustrating.