We call this "Open Source Intelligence." 85% or more of all classified stuff is generated using it.
Think about this from a family perspective... If you have something senesitive to your family that you would not want others knowing about, how hard would it be to deduce that issue/item/problem/person using information that is freely available: Ads on your car (like shown), the mail that is delivered to your home, what you say in public, etc, etc, etc. Now the chances that someone is trying to harm your family are minimal and taking all sorts of measure to secure info like this may be.. well.. paranoid. But then just by the nature of this forum I don't think many of us count on statistics and chances to keep us safe.