I disagree with some of this, in fact with a lot of it, though it does seem that when Evan describes the mechanics of those who have moved to digital reading, he is on the money!
While I see the logic behind this understanding – I posit a slightly more nuanced definition of what is happening: Ebooks aren’t cannibalizing print books — consumers with ebook reading devices are, as a rule, no longer buying print books. Subtle? Yes, but from a commercial publishing point of view this is a crucial difference between seeing a direct correlation between ebooks and print books and understanding what happens to a customer when they make the switch to reading devices.
via Ebooks Don’t Cannibalize Print, People Do « Black Plastic Glasses.
Eoin Purcell's Blog 
You may also be interested in this article from the Telegraph, Eoin, which details the results of a recent poll that suggests 95% of Brits prefer paper to ebooks. Apologies if you’ve seen it already! Of all the book bloggers I know (and that’s a fair few), none of them has shifted completely to digital in the wake of buying an ereader.
http://www.telegraph.co.uk/technology/news/7734166/The-majority-of-Britons-are-still-wedded-to-CDs-DVDs-and-books.html
Thanks Litlove,
Partly I see this as being an issue of economics. As a dedicated print reader who only occasionally reads full length books digitally (I read far too much on screen though in terms of short and mid length pieces!) I worry about what will happen to book prices if this 10-20% slide occurs. I think we underestimate the impact even that much of a loss in revenue would affect print.
I’ve been writing a post about it, but it is a frustrating one!
Eoin