Richard Muscat, writing at Serious Simplicity:

My contention is that “Free” as described and used in many contemporary web-based businesses is a non-business model that is not only broken, but actively harmful to entrepreneurship. Free rarely works, and all the times that it doesn’t, it undermines entrepreneurial creativity, destroys market value, delivers an inferior user experience and pumps hot air into financial bubbles. I think this piece hits it out of the park. Why should you price your product as a pay-for-service or good? This article lays out all of the reasons and why free should never be your decision.