Point the First: "Not everyone who illegally downloads your book would have bought it, so you shouldn't act like they would have."
True! That being said, I know enough people who have illegally downloaded books and then bought them, or have told me to my face (or via email) that they were planning to buy the book, only then got it for free, that I feel some consideration of the number of illegal copies is warranted. Just going off what I do know, I tend to assume about one person in ten represents a "lost sale." This accounts for new readers only, not people downloading copies of books they already own.
Point the Second: Downloading copies of books you already own is a morally gray area.
True. I completely understand and sympathize with people who download virtual copies of books they already own. Unfortunately, a) I don't own the e-book rights to my books right now, and thus can't say "sure, have a PDF with proof of purchase," and b) the methods for getting those downloads are non-legal. There's not a private literary speakeasy where you have to send in a photo of yourself with your legal physical copy before you get the download link. And so while I can understand the moral ambiguity of it all, I can't endorse the practice.
Point the Third: It's not piracy, it's copyright infringement.
Okay, true. For precision of language, I should call it copyright infringement. But the people who sometimes post intentionally inflammatory things on message boards aren't actually trolls, they're just being mean. In some cases, the prevailing language of the land is going to win out over precision. I apologize for any confusion.
Point the Fourth: "Does this mean you don't like me because I initially read your book in a sub-legal format?"
Did you buy the book? I mean, really, that's where my concern is here: In whether I can feed the cats. I first discovered the X-Men because my friend Lucy had an older brother who wasn't careful with his comics, and I didn't pay for those, either. As I said above, I can't condone illegal downloading, but once you've paid for the material, I lose all personal animosity.
Point the Fifth: Books and music aren't the same.
Most the research on illegal downloads has been in the music arena, and the numbers aren't the same. According to iTunes, the single song I have listened to the most often is the cover of "Livin' La Vida Loca" by Spork, which I have listened to 342 times. The single book I have read the most often is IT, by Stephen King, which I have read, if guessing generously, eighty times in the last twenty years. Many people don't re-read, or do so only sparingly. So saying that illegal downloads increase sales when you're only looking at music is like saying that breeding mice increases the elephant population.
Point the Sixth: Cory Doctorow does it.
Cory Doctorow is also recognized by my spellchecker, which doesn't recognize my name. He chose to distribute over the Internet, and it worked out awesomely for him. He's also doing Internet-savvy fiction, with a keen edge of interest for the online crowd. I write urban fantasies about women with silly names. We don't have the same target audience; it's mice and elephants again.
I'll come back and participate in the discussion more one on one later. Now? DayQuil and sleep.