The advances in positioning technologies and the emergence of geolocation standards opens up to the development of innovative location-based services (LBS), e.g., web-based LBS. These services challenge existing privacy protection solutions. For example, the position information is provided by a third party, the location provider, and this party may be not fully trusted. In this paper, we analyze the web-based LBS model. Then we outline the privacy-aware geolocation strategy which minimizes the interaction with the untrusted location provider by caching the information that is useful to determine the position in proximity of the private positions, e.g., home, which have been already visited. The deployment of this strategy requires investigating several issues and novel tools. The objective of this paper is to discuss the technical challenges and suggest directions of research towards a comprehensive privacy-preserving framework. To our knowledge, this is the first work on privacy protection against untrusted location providers.