The small software and hardware companies realized a broad range of Location-based Services (LBS) capabilities for both mass and niche markets and laid down the foundation for a new generation of LBSs. The emergence of GPS-capable mobile devices, the advent of the Web 2.0 paradigm, and the introduction of 3G broadband wireless services are among the enabling developments. The emergence of GPS-capable mobiles made the users to write small applications passing location data to a central server to make their location available to other users. The self-referencing LBSs are services in which the user and target coincide, while cross-referencing LBSs exploit the target location for service-provisioning of another user, thus requiring stronger privacy protection. The demand for user-centric LBSs, driven by the users themselves to enable the effective exchange of user-generated content among peers, called for terminal-based localization estimation and user-centric management of location data.