Data mining with google trends

I have being a fan of Data mining for quite some time. I recently read the book “Everybody Lies: Big Data, New Data, and What the Internet Can Tell Us About Who We Really Are” by Seth Stephens-Davidowitz.
Here, Stephen tries to tell us that a huge amount: of information can be gotten from using free tools like google trends. Wikipedia defines google trends as

Google Trends is a public web facility of Google Inc., based on Google Search, that shows how often a particular search-term is entered relative to the total search-volume across various regions of the world, and in various languages.