This is an odd site – http://www.pleaserobme.com/ For a while, it was probing twitter looking for references to being away accompanied with location information, and publishing a list of empty residences.
In particular they were concerned about foursquare, the ‘game that rewards you for doing interesting things’. In this case, interesting things being location based tagging. Its all based on GPS in the smart phones that the foursquare app uses to tell the site where you are. And then the site can tell you where your friends are, what they are up to and information about the locations you are visiting.
Whether we like it or not, location based services are here to stay. However, pleaserobme does have a point – if the phone knows where you are, and the website can tell someone else, then they can decide that where you are not, is at home.