In Sept I attended HCI 2010 24th BCS Conference on Human Computer Interaction.
1. Hansen, M., Shneiderman, B, and Smith, M. A., Analyzing Social Media Networks with NodeXL: Insights from a Connected World, Morgan Kaufmann Publishers (2010).
He is clearly now impassioned about social participation  and specifically getting the HCI community to advocate and lobby government on the various challenges we face. He has run a couple of workshops on "Technology-mediated social participation
". The website has details of the events along with links to various position papers. As these comes from people working at funding agencies and industry they are worth a read.
 Preece, J. and Shneiderman, B., The Reader-to-Leader Framework: Motivating technology-mediated social participation, AIS Transactions on Human-Computer Interaction 1, 1 (March 2009), 13-32, available at http://aisel.aisnet.org/thci/vol1/iss1/5/