Via Masnick, another data point that seems to suggest that giving away your books for free via the Internet really does boost sales of hard copies.
Neil Gaiman, who was part of Harper Collins experiment with giving away free ebooks, discovered (like so many others) that giving away the free ebooks helped increase sales. And, of course, it wasn’t just for the one book that was offered for free, but across all of Gaiman’s works. The other bit of information is that, as we expected, HarperCollins found that many people were not at all happy with all of the restrictions it put on the ebooks (including that you had to read it on their website rather than download it