I have set my home and work addresses in Google Now and they kept knowing where I was. Finally I realized I had enabled location history on Nexus 7. Privacy concerns is a very personal thing and I generally care how much Google knows about me. So I have turned off both location reporting and location history. But my previously recorded history is still available to Google services.
How to Delete Location History in Google Now on Nexus 7
* You have to do that on a desktop computer.
* Open location history and log in.
* The web page will show your location history for any date. Click "Delete all history" and "OK".