Found this overview of key arguments at the Shared Design Alliance:

“Placing design information in the public domain has the following benefits:

1. Lowers Entry Barriers by Providing a Platform for Low-Cost Experimentation.

The success of Google is based on two shared designs. The first was the published design of the IBM compatible personal computer, which led to the explosive growth of an industry and eventually to very low-cost consumer computing hardware. Google’s founders networked thousands of cheap computers together using Linux, a free operating system that they modified to perform internet searches at higher speed and lower cost than their competitors. Without the PC standard and Linux, Google would not be the rapidly growing tech company it is today. Shared designs allow innovators to add small improvements without reinventing the wheel, and this freedom can lead to great things.

2. Allows Collaboration Across Boundaries.

Most of today’s best research comes from connecting disciplines which seem to have little in common, and many new ideas come from people who happen to be involved in multiple fields. Shared designs break down some of the traditional organizational boundaries, allowing innovators to collaborate more freely. ZeroPrestige.org, a website for sharing the plans of kites used in the sport of kiteboarding, allowed aerospace engineers to collaborate with extreme sports enthusiasts to produce superior kite designs that are rapidly capturing the market. When people with diverse skills, knowledge, and experience cooperate, the resulting ideas are often revolutionary.

3. Accelerates Technical Evolution.

The usual model of research requires a team of researchers in the same organization working toward a single goal. Shared designs allow multiple teams in multiple organizations to pursue different goals at the same time. For example, the relatively easy sharing of recipes allows thousands of cooks to develop dishes to satisfy the public’s changing tastes much faster than makers of packaged food. This type of parallel development increases the speed of innovation and allows technologies to follow societal changes faster than large organizations are able to.

4. Increases Societal Wealth.

A big part of the world’s wealth is based on technologies that are well understood and belong to everyone, such as telephones, wheat farming and concrete. In today’s climate of fast-paced technological growth, it’s easy to forget how many designs we already share, and the incredible value we derive from their slow but steady improvement. In many areas, we can’t afford to wait 20 years for patents to expire, and we would derive more total benefit from releasing ideas into the public domain now.

5. Coordinates Efforts to Benefit Underserved Communities.

Shared designs work best in areas where needs are diverse and pressing and where there is a relatively small opportunity for profit. For example, small-scale energy production, products for the developing world, seeds and agricultural techniques and many areas of the medical industry match this description. These are also areas served poorly by expensive R&D and mass production, and may be served better through a different model.

Similarly small (but not disadvantaged) communities have been successfully served commercially through methods that seek the “long tail.” This term describes the area of a normally distributed curve of demand for products excluded by a “one size fits most” model of product selection. Books or music CDs, for example, for which there is little demand, will rarely be produced or widely available through traditional venues. When the marginal cost of distributing a single copy of a song is reduced to that of distributing the one hundred thousandth, or the small demand in a single local area is aggregated, these items can be commercially distributed and available to the small communities that desire them. The SDA seeks to nurture innovators, entrepreneurs and activists by attacking the barriers that separate them from the communities they might serve, or that separate them from the solutions they seek.”

The Shared Design Alliance (SDA) advocates for and demonstrates the value of sharing the design information contained in physical products, and produces infrastructure to make design sharing and modification easy and efficient.