Give away your e-book and sell more hard copy books?

Earlier this year I wrote about the correlation between the sales of e-books and hard copy books. The well-know New York Times technology columnist and "Missing Manuel Book" - writer David Pogue wrote in June an article on the this subject. His perspective has to do with copyright and pirated use of e-books and fits the discussion that creative work will sooner or later become freely available via the Internet. Paul Krugman wrote an interesting but much discussed article on this model already used by the Grateful Dead.
In considering free e-books Pogue refers to three possible relations that might exist: giving away e-books for free will boost sales of the print edition, selling e-books is the only legitimate way to buy electronic versions and e-books will kill income of printed books. Pogue refers to two interesting variables: the awareness of the author (less-known authors supposedly benefit more from the free exposure and attract new readers of the printed version), and the genre of the book (do you read science-fiction on a screen?). One of the people who reacted to the story was Kevin Kelly who suggested to have a test with one of Pogue's books. His prediction is that his e-books will not be duplicated as much as imaged and elevate, or at least not depress sales of the print version. Pogue's publishing company started the test this month and I'm curious to see whether the results will confirm what the National Academies Press concluded earlier this year.