A common concern with digital publishing is the loss of revenue from pirate copies. Truth is, there has always been piracy when it comes to books, the only difference now is that the digital age makes it easier. That said, I doubt most books, or authors, will ever face that concern as they won't be popular enough to pirate.
As authors, we can either embrace the digital age, or try and lock it out.
Many gaming companies use Digital Rights Management (DRM) software to ensure their digital goods are not copied, but it doesn't work. Any determined pirate can get round that, while it causes grief to some users and is part of the cause for the decline in sales of PC games.
Other ways to lock people in are proprietary formats, such as the Kindle file format, which prevents a purchaser from using the file on another ereader. This, too, can cause irritation among people who have bought a book to read and want to lend it to a friend.
What all the anti-piracy measures fail to take into account is that most people are not crooks and have no intention of making money out of another's work. They just want to read the book, then file it, give it away or, occasionally, sell it.
There is an answer: The Creative Commons License (CCL)
The books I issue use this and it has several layers allowing people to use it in various ways depending on what you allow. For books, I allow people to share with friends and family, but not to sell or adjust it, which is the highest level. Essentially I am allowing people to do with my ebooks, exactly the same thing they do with print media.
Crooks will always be crooks, but by refusing DRM on an ebook and using the CCL, I'm not assuming everyone is a potential thief.
Sometimes, I feel, I have to give a little to get a little. For me, that means trusting my readers.
More information can be found on the Creative Commons website: http://creativecommons.org/licenses/