eReader DRM, Mobipocket DRM and Microsoft .lit DRM provide no protection against copyright infringement. Simple scripts that will remove the protection from the files are readily available. And it only takes one person to remove the DRM and post the file.
Seriously - DRM provides no protection.
Adding some text to the book emphasizing that the book is not free but must be purchased, giving the URL of your web site, will help. That way if a copy does get passed along, you might well make a sale in the end. It's amazing how ignorant many people are about what's the right thing to do.
Originally Posted by Richard Maseles
And I have to at least look into the possibility of DRM, although I am prejudiced against it, solely on pain in the butt aspects. But because I'm not giving my products away, I have to assume that there will be some theft, and it's only prudent to look into minimizing that theft.