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"The man who saved Iran" might be the most hyperbolic thing blogged about Jared Cohen this summer, but not by much. The huzzahs that greeted the news that the 28-year-old State Department staffer called on Twitter to delay a service blackout during the height of the Tehran street protests threatened to obscure the true complexity of Foggy Bottom's new, technology-enabled approach to diplomacy. Secretary of State Hillary Clinton spoke of it herself in a commencement speech at Barnard College on May 18. "With social-networking tools that you use every day to tell people you've gone to get a latte or that you're going to be running late," she said, "you can unite your friends through Facebook to fight human trafficking."

And in her agenda-setting July 15 speech to the Council of...