NSA surveillance exposed by Snowden ruled unlawful

Also problematic is the extremely large number of people from whom the NSA collected telephony metadata, enabling the data to be aggregated and analyzed in bulk... A couple of examples illustrate this point: A woman calls her sister at 2:00 a.m. and talks for an hour. The record of that call reveals some of the woman's personal information, but more is revealed by access to the sister's call records, which show that the sister called the woman's husband immediately afterward. Or, a police officer calls his college roommate for the first time in years. Afterward, the roommate calls a suicide hotline. These are simple examples; in fact, metadata can be combined and analyzed to reveal far more sophisticated information than one or two individuals' phone records convey.