The London-based Networked Neighbourhoods has released a set of extremely important studies on "the social impact of citizen-run online neighbourhood networks and the implications for local authorities."
This connects to the heart of the use of open government by the public - you need online public spaces where citizens in the context of governance (particularly with elected officials who can say, these are MY voters talking) are asking for information and generating new public opinion. These online spaces be they "community sites" or a dozen of the different technologies and approaches, are essential for everyday citizens to discuss government and broader community affairs. These exchanges generate general demand for and often specific requests for government information.
Also, from a DIY perspective, it is though these spaces that we see critical mass local adhocracy or coproduction opportunities emerge. (This what we see increasingly here http://e-democracy.org/nf at the neighborhood level.)
Very very in-depth - report links and my take on their work:
Included in the blog post above are updates on the proposed "Meet Your Neighbors Online Week" and the Neighborly nearest neighbors social networking idea.