Social media platforms such as Twitter pose new challenges for decision-makers in an international crisis. We examine Twitter's role during Iran's 2009 election crisis using a comparative analysis of Twitter investors, US State Department diplomats, citizen activists and Iranian protestors and paramilitary forces. We code for key events during the election's aftermath from 12 June to 5 August 2009, and evaluate Twitter. Foreign policy, international political economy and historical sociology frameworks provide a deeper context of how Twitter was used by different users for defensive information operations and public diplomacy. Those who believe Twitter and other social network technologies will enable ordinary people to seize power from repressive regimes should consider the fate of Iran's protestors, some of whom paid for their enthusiastic adoption of Twitter with their lives.