-The Privacy and Civil Liberties Oversight Board’s 2014 review of the NSA “Section 215” phone-record program found no instance in which the dragnet produced a counter-terror lead that couldn’t have been obtained with targeted subpoenas. https://en.m.wikipedia.org/wiki/Privacy_and_Civil_Liberties_...

-After Boston, Paris, Manchester, and other attacks, post-mortems showed the perpetrators were already in government databases. Analysts simply didn’t connect the dots amid the flood of benign hits. https://www.newyorker.com/magazine/2015/01/26/whole-haystack

-Independent tallies suggest dozens of civilians killed for every intended high-value target in Yemen and Pakistan, largely because metadata mis-identifies phones that change pockets. https://committees.parliament.uk/writtenevidence/36962/pdf