Online Social Networks (OSNs) provide new ways for people to communicate with one another and to share content. OSNs have become quite popular among the general population. Their rapid growth has raised concerns about privacy and security on the one hand but increased efficiency in solving everyday online tasks on the other hand. Many predict that the OSNs of today provide a glimpse of the future Internet infrastructure. Whether or not that will be true is difficult to say but what is certain is that privacy, integrity, and security issues related to the world wide web will be as important then as now. This article presents a method for improving efficiency and security of E-mail applications by focusing on one of the core concepts of OSNs; the user profile, which both includes private and public information that the user shares to different parties and the social interaction between users.We present a generic method for comparing user profiles, by measuring the distance between user profile or user vectors and an algorithm that uses this method for prioritizing the E-mail inbox. We report on an experimental case in which the proposed method is used in conjunction with social information from Facebook to demonstrate the applicability as well as to motivate its theoretical foundation.