This paper presents the Linked Internet UI Concept, or LinkedUI for short, as a holistic user interface concept to facilitate social interaction on mobile devices. It aggregates social events from social networking services and communication channels and uses hypertext navigation for presentation and interaction. We describe the concept design principles, highlights of the design, and the prototype implementation. We conducted a user study to compare LinkedUI with the benchmark of web applications running in a web browser to follow their friends' activities in Twitter and Flickr and two other optional services on mobile devices. The study results reveal that the users performed tasks faster in LinkedUI and also liked it more than the benchmark. These findings support the design principles of LinkedUI in facilitating social interaction via mobile devices.