But it seems to me that the key variable is finance, not incentives. To take the example of a person writing a book, that person may be 100% motivated, and may need no financial enticement as an incentive. However, without an ability to finance research travel and living expenses during the long period of time it takes to write a good back, that book will not be produced. So, from a production perspective, the issue is finance, not motivation.

Conventionally, a book would be produced by a publishing company providing initial financing, in exchange for an ability of that company to make a profit by limiting access to the book to those who pay - to extract rents by limiting access. As Eben noted, that industry is changing, and some companies have shown an increased willingness to allow Creative Commons licensing.

Wikipedia and free software production tackle the finance problem in an different way. Many small donations of labor spread the cost. The right technology and social institutions enable the effective coordination of all these efforts into a whole greater than the sum of its parts.

I think the point I'm building towards is that even if we hold motivation constant, and assume highly motivated actors who need no monetary incentives, we still need to figure out financing mechanism that will work for the particular thing we are trying to produce.

For example, the Wikipedia could not be produced until the technology and social institutions existed to tap the motivation of many people and assemble it into a whole at low cost. So the threshold issue was finance.

The free software/wikipedia model of synthesizing collective efforts will work beautifully for many projects. But there are other projects which depend more specifically on the work of a single person over a long period, rather than the aggregation of many microworks. A musician or novelist or researcher doing such long-term, relatively individual-centric work could support herself by working part time, but we might as a society decide we want to have some of these functions performed full-time. If the current knowledge industry approach of limiting access to products to extract rents is abandoned, it will need to be replaced by a better financing mechanism. This might be a tax, or some type of subscription, or foundation grants, or something else entirely.

But as a starting point, I think it's important the purpose of clarity to distinguish incentives versus finance. I think the two are sometimes conflated in discussions about knowledge production and sharing rules - for example, finance is often treated as if it were an incentive (and it may be in some cases for some actors).

However, by distinguishing the two concepts, we can evaluate them each more clearly. The objection against sharing from incentives, I think, has little merit. However, the issue of finance is an important one, I think. There are some terrific sharing-friendly financing mechanisms, such as with Wikipedia and free software. But I think a lot of work remains in spreading access to and understanding of that type of collective effort model as well as developing sharing-friendly financing mechanisms for other more individual-centric kinds of projects.