Iraqi Prime Minister Nouri al-Maliki is welcomed by Vice President Biden in Washington on Wednesday. Maliki is asking for U.S. military hardware to fight radical groups behind a recent surge in violence in Iraq. Cliff Owen/AP hide caption

itoggle caption Cliff Owen/AP

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

itoggle caption Steve Greer/iStockphoto.com