Here is a good video showing how it works, and the strengths of Bigquery:
Now there is something that bugs me about it: It is the privacy issue. How Google may assure the privacy of the data it will process?
Also there is another correlated question: How is Google making money out of it? It doesn't seem clear if the service is free or not. But Google is used to propose free services in order to get from users' data to propose keywords.
What do you think about it?