A growing number of agents from internet entrepreneurs to celebrities are entering an increasingly crowded development space, bringing with them ideas and approaches that emphasise market-oriented modes of grant-making. The discourse and practices of the new philanthropy, as it has come to be known, as well as the organisational forms which underpin programmatic design, is increasingly informed by a particular form of managerialism, labelled philanthrocapitalism by Bishop and Green (2008). This is hailed as a harbinger of dynamism to the supposedly staid and partly ineffectual third sector, which, its critics attest, has failed in its mission to curb entrenched poverty. For reasons that are not always clear, however, examination of these actors â- new foundations, venture philanthropists etc â- has largely flown under the radar of international political economy and development studies scholars who have tended, perhaps for reasons of sectoral scale or an 'enemy perception' as Knorringa and Helmsing (2008) have described it, to ignore the growth of social entrepreneurship in favour of empirical analysis of NGOs and programmes of official development actors such as international organisations and bilateral agencies. This paper investigates sectoral 'blending' in international development, a process whereby private sector approaches are diffused by 'for-profit' social enterprises such as Google.org, the Acumen Fund and the Skoll Foundation with the aim of increasing performance and 'impact'. It explores what this nascent paradigm might mean for the trajectory of development cooperation. It is found that a not-so-quiet revolution is taking place in philanthropy in the US. Despite the hollow platitudes that sometimes accompany this phenomenon, it is argued that it has significant implications for development policy and practice by both challenging and, somewhat counter intuitively, complementing the participatory model that has dominated development discourses since the late 1980s.