Read My GPS Logs by Aaron PareckiAaron Parecki (Aaron Parecki)
I've had a fascination with maps for as long as I can remember. During family road trips to San Francisco I remember tracing our route on a map with a highlighter in real-time. Many, many years later, I am able to trace my route automatically with a GPS receiver on my phone. https://aaronparecki.com...
Aaron has really done some awesome map related work with his GPS tracking. Looking at just his personal map data for a year or two will give you an idea about how much other corporations can gain from tracking millions of people this way.

Looking at some of the map pins like for Target on his map will tell you that Google could potentially be using aggregate data about visits to companies as a way of knowing how well or poorly a company is doing and then using that data to make bets for or against companies in the stock market. This could give them the ability to front run investments if they wanted to.