The Center for Democracy and Technology issued a small but profound report last week noting that police can buy data about individuals from third parties that in former times would have required a court order to obtain. That includes cell phone location data.(1)
If you want a mild shock and live in the US, try searching for yourself in fastpeoplesearch.com. You have to get past the I-am-not-a-robot task to gain access, but once there, the amount of information about your current and past and the accuracy of that information is pretty intimidating. There’s a clear reason never to use a street on which you have lived as a password for anything.
The US lacks the privacy laws that Europe provides. Unless, of course, you’re a member of Congress. They live by different laws than the rest of us.