ARCOMEM is a EU-funded research project. It is about memory institutions like archives, museums, and libraries in the age of the Social Web. Memory institutions are more important now than ever: as we face greater economic and environmental challenges we need our understanding of the past to help us navigate to a sustainable future. This is a core function of democracies, but this function faces stiff new challenges in face of the Social Web, and of the radical changes in information creation, communication and citizen involvement that currently characterise our information society (e.g., there are now more social network hits than Google searches). Social media are becoming more and more pervasive in all areas of life.