Some 30,000 people showed up to hear a speech by Mir Hussein Moussavi, a reformist candidate for the Iranian presidency -- and they hadn't been paid, fed or bussed in, tactics used by the incumbent President Mahmoud Ahmedinejad. The supporters showed up mainly thanks to the campaign taking place on Facebook. The social networking tool is rocking the campaign so much that the Iranian government blocked access to it last Saturday; restoring it yesterday. For more on the new campaign tools and an analysis of the Iranian election, we turn to Jon Leyne, the BBC's correspondent in Tehran.