Can a free book be a bestseller?

I love free stuff, particularly when it comes recommended by someone whose opinion I trust. Hence a free copy of Steve Pressfield’s new book Do The Work landed on my Kindle yesterday care of Seth Godin. (Pressfield is the author of War of Art).

Godin wrote in an email yesterday:

Of course, subscribers to the Domino blog already knew about the new book and got it for free in digital form. In fact, it’s already a bestseller. Not too late to join in…

Which begs the question as to whether something given away for free can actually be a bestseller? Does the consideration for the sale have to be greater than zero? Does an online transaction necessarily have to include money? Or is an exchange of, say, contact information in return for a book enough?

Your answer those (and other) questions is critical to how you approach marketing in the digital space.