She just nails it:
Opponents of the free-content argument too often reject the idea that free content is the future simply because they don’t want it to be true.[...]
“No man but a blockhead ever wrote except for money,” Samuel Johnson said, and that attitude has had a good two-century run. But the Web is full of blockheads, whether they’re rate-busting amateurs or professionals trawling for speaking gigs. All this free stuff raises the real standard of living, by making it ever easier for people to find entertainment, information and communication that pleases them.
Business strategy, however, seeks not only to create but to capture value. Free is about a phenomenon in which almost all the new value goes to consumers, not producers. It is false to assume that no price means no value. But it is equally false to argue that value implies profitability.
Enjoy the whole article, it's more than just a review. It offers Postrel's usual keen insight, helping us to read between the lines.