http://www.slate.com/articles/technology/future_tense/2015/10/research_suggests_google_books_isn_t_as_helpful_as_some_believed.html

Sometimes it isn’t enough for data to be big. Consider Google Books, a searchable archive digital archive of millions of texts spanning the history of the printed word. This enormous corpus has inspired researchers to rethink the ways we map the history of language, allowing them to make sweeping claims about the evolution of language and culture. Researchers have, for example, used it to chart changing patterns of celebrity culture or to propose that moral language is waning. The trouble is, we may be arriving at those assertions a little too glibly.