This research shows the power of cell phone metadata. From an article by the author:
Yemen has experienced an array of violent incidents and political turmoil in recent years, ranging from al Qaeda militant attacks to drone strikes, Arab Spring protests, and now Saudi Arabian air strikes. Call patterns can capture political or violent activities as they unravel in real time. For instance, there was a significant increase in the number of local calls following a nighttime drone strike on Friday, October 14, 2011, in Shabwa Province, which killed Ibrahim alBanna, media chief of al Qaeda in the Arabian Peninsula, along with eight others. Several additional drone strikes are detectable through significant spikes in local call volume at the time of attack, including a May 5, 2011, strike in Jahwa that killed two brothers affiliated with al Qaeda. A May 10, 2012, attack that killed eight al Qaeda militants in Jaar and a May 25, 2010, attack in Wadi Abida that killed two militants and four to six civilians.
Because call data records are geolocated, researchers can also examine them to assess users’ mobility. This can be a very useful tool to detect protests and other events that entail notable mobilization. On Friday, June 3, 2011, for example, the day President Ali Abdullah Saleh was attacked at the presidential palace in connection with the Yemeni Arab Spring, the number of people near the palace spiked around the time of the incident. Several other protest events linked to the Yemeni Arab Spring are captured by high levels of user mobility, including the string of Friday protests during 2011 when protesters would gather at Sanaa University Square and government supporters would stage their counterrallies at Sanaa’s Tahrir Square.
From an interview:
So for instance, if you are interested in larger political patterns, such as who shows at a demonstration, or who takes a leadership role in a demonstration…by having this data, you know what he’s like. You know where he lives. You know who he calls and who his friends are. You know if he’s Shia or Sunni, depending on what holidays he makes calls. You know if he’s rich or poor depending on how much phone credit he uses.