Clay Shirky gave a terrific talk at the RSA last month.
Always good value Shirky talks about the ideas in his new book Here Comes Everybody: The Power of Organizing Without Organizations, illustrating his points with stories about collective protest with the aid of Web technologies that couldn't have happened without those technologies - students v HSBC, students v dictator in Belarus, business v mafia.
The interesting thing for me was that he also described the moment he stopped being a cyberutoptian. This was when a student who worked for a teen magazine explained they had decided to shut down their online discussion forums because they were being dominated by pro-anorexia girls, evangelising starving themselves. Yet when the forums closed down the girls just moved to another web site. It struck Shirky fairly forcefully that the destructive use of the technologies was not just a side effect but a feature. Just as they can be used to peacefully protest against brutal dictators by eating ice cream in Minsk, they can are are being used by organised groups for much more socially and politically destructive purposes.