In many underserved communities, however, neither the invisible hand of the government nor markets cater to even the most basic needs of their members, resulting in structural and behavioral barriers to the community's growth and development. These barriers are addressed by products and services engineered by social entrepreneurs.
Social Entrepreneurship is an emerging and evolving concept. This article from an Indian Summit called Sankalp 2010 provides a great snapshot. It talks about what Social Enterprise is, an example in Mumbai of the “Dabbawallas,” and the need it fills.