The cover story in Wired right now is Free! Why $0.00 Is the Future of Business.

But free is not quite as simple — or as stupid — as it sounds. Just because products are free doesn’t mean that someone, somewhere, isn’t making huge gobs of money. Google is the prime example of this. The monetary benefits of craigslist are enormous as well, but they’re distributed among its tens of thousands of users rather than funneled straight to Craig Newmark Inc. To follow the money, you have to shift from a basic view of a market as a matching of two parties — buyers and sellers — to a broader sense of an ecosystem with many parties, only some of which exchange cash.
The most common of the economies built around free is the three-party system. Here a third party pays to participate in a market created by a free exchange between the first two parties. Sound complicated? You’re probably experiencing it right now. It’s the basis of virtually all media.

You have to read the story to have that title make sense to you.
…and I think The Beauty Of 99¢ iPhone Apps (via) shares a lot of the same thinking.