In the midst of the June 2009 post-election protests in Iran, when President Obama refused to speak out on behalf of the advocates of freedom, Cohen reached out to Twitter founder Jack Dorsey and urged the company to reschedule its planned maintenance of the website so that Iranians could keep tweeting. Given that all other forms of communication had been blocked or shut down, Twitter was one of the only ways for people inside of Iran to get information to the outside world. It also became an important way for people around the world to join the protests by disseminating proxy and circumvention tools. When the New York Times broke the story, it came at a time when the Obama administration declared that there would be no meddling in Iran. Cohen's involvement drew international interest not just because at the time it was the most robust action taken by the U.S. government in response to the protests, but also because Cohen had spent time in Iran and written about the possibility of technology being used for social upheaval in his book Children of Jihad.

Cohen is author of several books. His first, One Hundred Days of Silence: America and the Rwanda Genocide, was published in 2006 by Rowman & Littlefield and chronicles U.S. policy toward Rwanda during the 1994 Genocide. His second book, Children of Jihad: A Young American's Travels Among the Youth of the Middle East, was published by Penguin Books (Gotham) in October 2007 and has also been published as an audio book and translated into Dutch and Italian. Cohen's work on Children of Jihad was selected as one of the "Best Books of 2007."