Despite some people's conviction (see Howard Rheingold) that cybercommunities could improve democracy, the jury is still out. We had an enormous number of cybercommunities, many of a political kind, in the period just preceding March of 2003 (when compared to what we had before 1995), and yet, a war most unjustified and unpopular at an international scale still took place despite all the weblogs blasting it.
I've written about this issue from different angles before: 1 and 2.