I made this point earlier: people who can afford a 2 books/week habit in (discounted) hardcover can certainly afford an e-reader and content for it, even under the agency model. But there are other factors involved in piracy.
(1) It's inconvenient. Way, way, way more inconvenient that pressing that button on the Amazon site that says send it through the cellular phone network to my kindle. Even if I have to select which kindle I want it sent to.
(2) It's not necessarily reliable, or high quality. I can't speak to what's out there right now, but if the formatting in the legit e-books leaves something to be desired, I seriously question whether illicit reformatting, un-DRMing and whatever else happens to it in the course of making it available for "free" is going to improve matters. I could readily imagine that at least part of the time, what you get when you get a pirated version isn't precisely the same as what you would get if you bought it.
Obviously, these factors have not stopped movies and music from being pirated. I'll just point to this, highly problematic survey:
While gadget buyers may tend to be young and male and piracy oriented, book readers tend to be older, female and, let's just say it up front, not so piracy oriented. The music and movie market tended to be younger and, um, broker. The book market tends to be older and better-resourced.
I think the piracy thing makes a better argument from a rhetoric standpoint than as a real threat.
But if e-book piracy convinces a bunch of young, male gadgety types to start reading, I have to regard that as not entirely negative.