Unlike many economists I have no view on the desirable size of government. I do not believe that 'taxation is theft', or that economic freedom is necessarily the most important consideration. To me it is the distance between government and people that is the matter of concern, especially as this distance seems to be widening in most democracies.
The gap would narrow if more people participated in policymaking. One reason, I believe, why we're not very interested is that policy is formulated in terms that are difficult to relate to outcomes that are meaningful to natural persons, as distinct from corporate bodies. Policymakers appear to concern themselves with decisions about funding for different government agencies, dispensing patronage to big business and other lobbies, presenting themselves in the best light ... almost anything, in fact, except outcomes that mean something to real people.
A government that issued Social Policy Bonds would, from the outset, have to concern itself with social and environmental outcomes. Its main role would be to articulate society's wishes regarding social and environmental outcomes, and to raise the revenue that would fund these outcomes. Unlike most of the current determinants of policy, the language of outcomes and the necessary trade-offs between them is comprehensible to people other than politicians, bureaucrats, lawyers and public relations experts. For that reason, more people would be drawn into policymaking - an end in itself, as well as a means toward getting greater public buy-in to the resulting policies.
Expressing policy in terms of outcomes, and the consequent closing of the gap between public and policymakers would be one valuable benefit arising from a Social Policy Bond regime. The other would be the much greater efficiency in achieving social and environmental goals once the market, rather than a handful of government employees, decides who shall achieve these goals, and how they shall be achieved.