Seth Godin has a short but sweet post (the best kind) up on the need to flip the way you think about free, abundance, and scarcity.
Seth was one of the first people to experiment with free and digital media and he has been a longstanding inspiration to me in this way of thinking. During the late 90s, he gave away a number of his books for free in soft copy before the book was published. In doing so, he built up a word of mouth phenomenon that drove the sales of the hard cover when it came out.
Seth has also had a long standing view that interruption based advertising is costly both in terms of media cost and brand cost. He believes that there are better ways to get people's attention and that giving things away for free is among the best of those ways.
This paragraph from his post that I linked to above outlines the basic idea:
We spent a generation believing certain parts of our business needed to be scarce and that advertising and other interruption should be abundant. Part of the pitch of free is that when advertising goes away, you need to make something else abundant in order to gain attention. Then, and only then, will you be able to sell something that's naturally scarce.
I like his example of Lululemon's free mass yoga events in Bryant Park. I bet that does sell a lot of yoga clothes.