Now proximity to a crime gives the police “probable cause” to obtain your data from Google. From Aaron Kesel at themindunleashed.com:
Google reverse location search warrants have privacy and civil liberties advocates concerned.

(TMU) — The Gainesville Police Department suspected an innocent man was involved in a burglary so naturally they requested that Google give them all of his location data.
Google’s legal investigations support team wrote to Zachary McCoy telling him that local police were demanding information related to his Google account. Google replied and said it would release the data unless McCoy went to court and tried to block the request, NBC reported.
The man then searched his case number on the Gainesville Police Department website where he found a one-page report on the burglary of an elderly woman’s home ten months earlier on March 29, 2009. Unfortunately for McCoy, the crime occurred less than a mile from the home that he shared with his two roommates.
Caleb Kenyon, McCoy’s lawyer, said he was subject of a “geofence warrant.” A geofence warrant is essentially a virtual dragnet over crime scenes where police request to sweep up Google location data drawn from users’ GPS, Bluetooth, Wi-Fi, and cellular connections from everyone who is near a crime scene.