That's the title of a paper by Kathleen Segerson recently published in the Applied Economics Perspectives and Policy. Although I think she under-estimates the power of factors like reputation and over-estimates the ability of government solutions to efficiently coordinate actions, she offers a useful discussion that we ought to have more often. The abstract:
Voluntary approaches have been used in a variety of contexts and for a variety of purposes in agriculture, including voluntary conservation programs and product labeling. This paper provides an overview of some of the general principles that emerge from the literature on voluntary approaches and their application in agriculture. The literature suggests that, to be effective, voluntary approaches must provide sufficiently strong participation incentives to a targeted population, clearly identify standards for behavior or performance that ensure additionality and avoid slippage, and monitor outcomes. Thus, reliance on voluntary approaches in agriculture is likely to be effective only if there is sufficient market demand for certain product characteristics, significant public funds are committed to pay for voluntary actions, or the political will exists to impose regulations if voluntary approaches fail.