This article holds that the role of Twitter inside Iran during the election protests of 2009 was greatly overstated.
From the article:
"As Mehdi Yahyanejad, the manager of 'Balatarin', one of the Internet's most popular Farsi-language websites, told the Washington Post last June, Twitter's impact inside Iran is nil. 'Here [in the United States], there is lots of buzz,' he said. 'But once you look, you see most of it are Americans tweeting among themselves.'"