If it the data is not useful to Google, why collect it in the first place?
If the data is not useful to the US Justice Dept, state attorney generals, and national, state, local governments, why subpoena it?
If the data is not useful to internet Adwords competitors, why subpoena it in civil cases?
Even the most ardent Google supporters recognize that the vast volume of data Google collects on individual users is viewed as data mining gold mine.
Due some research on Deep Packet Inspection and Doubleclick Cookies and the 1986 Electronic Communications Privacy Act.
FAQ: When Google is not your friend