The Wall St. Journal reports that "for the past 18 months, the U.S. has invested heavily in ways to collect and examine social-media postings on Facebook, Twitter and overseas regional networks as a source of overseas intelligence, according to Gen. Flynn and other officials. They say it could revolutionize "open-source" intelligence gathering—the kind that focuses on finding key data from publicly available sources, as opposed to intercepting private communications or stealing secrets."
"Officials said government computers can aggregate material from multiple social-media networks and scan massive amounts of information already publicly available to any computer user for trends and links."
"Even so, spycraft's newest offshoot is arousing concerns. To many, mining social media is fraught with risks of privacy violations of Americans. The National Security Agency, another Pentagon intelligence agency, has been sharply criticized for collecting phone records and other data. Others see in social media a vulnerability to adversaries who plant misinformation or mount deception campaigns."