Science Fiction writer, Cory Doctorow, wrote a piece for Forbes on the business value of giving his work away for free on the internet.

I’ve been giving away my books ever since my first novel came out, and boy has it ever made me a bunch of money.

How did I talk Tor Books into letting me do this? It’s not as if Tor is a spunky dotcom upstart. They’re the largest science fiction publisher in the world, and they’re a division of the German publishing giant Holtzbrinck. They’re not patchouli-scented info-hippies who believe that information wants to be free. Rather, they’re canny assessors of the world of science fiction, perhaps the most social of all literary genres. Science fiction is driven by organized fandom, volunteers who put on hundreds of literary conventions in every corner of the globe, every weekend of the year. These intrepid promoters treat books as markers of identity and as cultural artifacts of great import. They evangelize the books they love, form subcultures around them, cite them in political arguments, sometimes they even rearrange their lives and jobs around them.

Doctorow argues that eBooks are viral artifacts that want to be passed from one friend to another. He also says they are, in essence, ads for the printed and bound versions of his work, which many of his readers eventually purchase.