I. Introduction
With the spread of ubiquitous [1], pervasive [2], and ambient [3] computing, the focus on privacy within these areas
Recently the term everywhere computing [4] has also been introduced. Although all these terms can be viewed as synonyms, a particular term typically indicates a particular perspective, such as a physical distributed system perspective vs. a functional-oriented service perspective.
has also increased. The specific sub-group called location-aware systems has received quite a lot of attention. This is in part due to the growing number of social-network applications available on the internet, such as Facebook, MySpace and LinkedIn and their recent use of people's position as an important part of these social networks, in effect making them location-aware. Location can either be explicitly stated by the user in services such as Twitter or Facebook, or directly sensed though location-based services such as Google's Latitude.