Lazer, David, and Ryan P. Kennedy. 2015. “What We Can Learn From the Epic Failure of Google Flu Trends”. Wired, 2015.
See also:
21st Century Democracy

Abstract
Every day, millions of people use Google to dig up information that drives their daily lives, from how long their commute will be to how to treat their child’s illness. This search data reveals a kit about the searchers: their wants, their needs, their concerns - extraordinarily valuable information. If these searches accurately reflect what is happening in people’s lives, analysts could use this information to track diseases, predict sales of new products, or even anticipate the results of elections.