Mohamed Osman Mohamud, then 19, is shown after his arrest on Nov. 26, 2010, in Portland, Ore. Mohamud was convicted of planning to detonate a bomb during a Christmas tree-lighting ceremony, but his sentencing is on hold after revelations that investigators relied to some degree on NSA surveillance. Getty Images hide caption

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Google and five other companies sent a letter last month to members of the Senate Judiciary Committee supporting legislation to reform NSA surveillance programs. Marcio Jose Sanchez/AP hide caption

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Gen. Keith Alexander is director of the National Security Agency, whose duty, his office has said, "requires us to attempt to collect terrorist communications wherever they traverse global infrastructure." Evan Vucci/AP hide caption

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Former chief counterterrorism adviser Richard Clarke is a lead member of a panel appointed by the president to review the country's surveillance policies. Alex Wong/Getty Images hide caption

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Edward Snowden, who provided secret U.S. intelligence documents to several media outlets, may have duped as many as 25 NSA colleagues into giving him their login information, according to Reuters. He's seen here in an image from an October TV report. AFP/Getty Images hide caption

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Cell towers are constantly tracking the location of mobile phones. And that data, federal courts have ruled, is not constitutionally protected. Steve Greer/iStockphoto.com hide caption

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News of U.S. surveillance in Europe has met with distrust and anger; officials are heading to Washington to discuss matters next week. Here, members of an artists' group paint a mural called "Surveillance of the Fittest" on a wall in Cologne, Germany, on Thursday. Frank Augstein/AP hide caption

itoggle caption Frank Augstein/AP