Everyone who carries a cellphone generates a trail of electronic breadcrumbs that records everywhere they go. Those breadcrumbs reveal a wealth of information about who we are, where we live, who our friends are and much more. And as we reported last week, the National Security Agency is collecting location information in bulk — 5 billion records per day worldwide — and using sophisticated algorithms to assist with U.S. intelligence-gathering operations. How do they do it? And what can they learn from location data? The latest documents show the extent of the location-tracking program we first reported last week. Read...