In the decades to come, the phrase correlation does not imply causation made its way into textbooks and academic journals, while the social sciences were made over with newfangled statistics. By the 1940s, economists had devised a name for the insufficiency of correlations: They called it the “identification problem.” A flood of numbers in the postwar years may have made the anxiety more acute until its apotheosis in the present day, when Google, Amazon, and the other data juggernauts belch smoggy clouds of information and spit out correlations by the ton. “That may be as deep a sense of causation as they care about,” Porter says. “To them, perhaps, automated number-crunching stands for the highest form of knowledge that civilization has ever produced.” In that sense, the admonitory slogan about correlation and causation isn’t so much a comment posted on the Internet as a comment posted about the Internet. It’s a tiny fist raised in protest against Big Data.
http://www.slate.com/articles/health_and_science/science/2012/10/correlation_does_not_imply_causation_how_the_internet_fell_in_love_with_a_stats_class_clich_.single.html