There is a choice. View those who share books with each other electronically as thieves and "pirates", or as book fans. People share. It's human nature. When people share books (and music) with me, I value their opinion and enthusiasm far more than I do any advertising. I will borrow a friend's book, read it, and then go out and buy more of that author's work.
Why criminalize free advertising and exposure? If you want to end e-book "piracy", stop calling it "piracy".