Ubiquitous e-service is one of the most recent links in the chain of evolution that has characterized the different eras of the internetworking environment. In order to leap the trust barrier for the users to embrace these ubiquitous e-services, we present a collaborative iTrust e-service for exploring proximal collective wisdom in the ad-hoc ubiquitous environment. By highlighting the homophily of e-service participants, these isolated individuals can be treated as a group with proximity. Proximity thus enables ad-hoc e-service participants to contribute their strength for ubiquitous collective wisdom. Simulation outcomes for trust decision quality enhancement show significant improvement over traditional designs. The iTrust e-service makes it possible for users to collaborate with the nearby user groups for establishing a reliable and trustworthy interaction environment. It also facilitates and empowers the potential benefits of various ubiquitous e-service applications.Keywords Ubiquitous e-service . Trust . Proximal collective wisdom . Ad-Hoc ubiquitous environment 1 Challenges for ubiquitous trustworthy e-Service Current e-service applications focus more on centralized control aspect, where long-term historical data are collected and top-down design architectures are used to guarantee information service quality of e-service applications. Since Mark Weiser (1991) termed 'ubiquitous' as a new paradigm for computing in 1988, efforts have been concerted to develop and advance information technologies towards 'connecting, invisible calm and silent, and real' ubiquitous computing. The rapid growth of information systems technologies and networking has generated significant opportunities for streamlining decision-making processes and maximizing productivity through distributed collaborations. Emerging collaborative environments need to provide efficient support for seamless integration of heterogeneous technologies such as mobile devices and infrastructures, web services, grid computing systems, various operating environments, and diverse products. Such heterogeneity introduces, however, significant security and privacy challenges for distributed collaborative applications. In such a loosely-coupled open computing system, trust management has become essential, together with traditional cryptography techniques, for building a healthy collaboration among participating peers (or agents). Hence, ensuring trust in an ubiquitous environment is one of the most important tasks of the new networking paradigm. Recent work (McKnight and Chervany 2002) suggests that reputation based trust systems as an effective way for nodes to identify and avoid malicious nodes in order to minimize the threat and protect the system from possible misuses and abuses by malicious nodes in a decentralized overlay networks. Such systems typically assign each node a trust value based on the transactions it has performed with others and the feedbacks it has received.