Ben Shneiderman kicked off the conference with a keynote on Getting Serious About Social Media: Strategies for Increasing Civic Participation . He also spent sometime covering some of his past research which you will be familiar with if you know his work. He demonstrated a number of points drawing examples from his recent book "Analyzing Social Media Networks with NodeXL: Insights from a Connected World" . The following day his co-author Marc Smith tweeted a link to a NodeXL layout he produced overnight showing "Connections among the Twitter users who recently mentioned #HCI2010 when queried on September 8, 2010 scaled by numbers of followers".
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/