Tim O'Reilly blogging about when free distribution is the best approach. I love the example from Frank Herbert's "Dune," using the ecological example of "law of the minimum" - that growth is "limited by the necessary nutrient that is in shortest supply."

Quoted: A lot has to do with the ratio of possible consumers of the free product who might be converted to paying customers to the total market size. If I have awareness with .01% of the target market, giving copies away to raise awareness to 10% of the market, where 10% of those might convert (1% total) is a good deal. But if I have awareness with 60% of the target market, and give my product away, with a 10% conversion rate, I've lost a great deal.