It is encouraging to see this sort of more involved consideration of privacy undertaken so earl in the adoption curve of a new technology. The risks arise where the metadata used for augmented reality applications is user modifiable. Similar concerns could be raised for the proliferation of location services in web applications like Twitter and Flickr of course.
The linked post doesn’t suggest anything in terms of how to mitigate these risks, it just identifies some of the more plausible ones. I think the overlap with social networks may suggest a starting point, carrying into AR the idea of permissions so that users can decided how far and with whom editable metadata is shared.