It's Who You Know
An interesting book is Social Capital; Key Ideas by John Field (ISBN-10: 0415433037), Director of the Division of Academic Innovation and Continuing Education at the University of Stirling. Social Capital is a term which has been popularised by the American political scientist Robert D. Putnam, who defined it as:
features of social organisation, such as trust, norms and networks, that can improve the efficiency of society by facilitating coordinated actions