The NASA-wide version of Spacebook is based on a design for a public-facing version currently referred to as "OpenNASA v.2.0". My idea is to release the new Spacebook (built on Liferay opensource portal s/w) source code as open source so that other Agencies (across all sectors of gov't) can begin developing similar intranets and OpenGov 2.0 (public-facing) portals.
This would greatly facilitate social networking between the participating Agencies, allowing easy access between each portal, with the added benefit of being able to share gadgets, portlets and widgets between the gov't portals, and between similarly designed portals such as iGoogle, myYahoo and myMSN.
Future phases could allow access to academic and industry partners, with the end goal of eventually allowing access to the general public, per the OpenGov emphasis on citizen engagement.
The cost savings would come by attrition: i.e., older/ legacy sites would fall out of use in favor of the next-gen portals. Legacy apps and sites that still have value could be "gadgetized" with the most popular/widely used gadgets and widgets featured and shared. This model would greatly modernize gov't web. Most Agencies still develop sites using old technology and obsolete techniques, and as such we have fallen far behind private industry, with social sites like Facebook. Twitter and MySpace dominating.