In ubiquitous computing environments, service servers play a central role of actively providing information about a person to help people determine whether he is available for contact or not. A tradeoff exists in these systems: the more sources of data and the higher fidelity in those sources which can improve people's decision, the more privacy reduction. Alternatively, there is generally no a priori trust relationship among entities interacting in pervasive computing environments which makes it essential to establish trust from scratch. This task becomes extremely challenging when it is simultaneously necessary to protect the privacy of the users involved. In this paper, we first show how trust evaluation process of the user's system can be based on previous interactions and peer recommendations. A solution then relied on trust to control privacy disclosure is proposed that depends on pre-defined privacy policy. Several tuning parameters and options are suggested so that end-users can customize to meet the security and privacy requirement of a ubiquitous system.