The question was posed and addressed by Chris Anderson. By free, he means free of charge: that’s the focus of his book in progress.
Glyn Moody is more interested in free as in free/open source software (and genomics, and…). He points out that most of the free (of charge) economy is also part of the free (open source) economy.
What struck me is the extent to which the ecosystem that has grown up around GNU/Linux dominates everything else in this admittedly back-of-the-envelope calculation: $30 billion out of a rough $50 billion. Which confirms the extent to which open source continues to be the bellwether in this area – the first and still best example of how to make money by giving stuff away.
Both Chris and Glyn use money, and in particular the US$, as the measure of size. I’d be interested to see other measures of the free economy: person hours, people affected, etc.