Introduction
Online social networks (OSNs) have reached major importance due to their increased usage and ubiquity, rising membership, and presence in the media. Allowing their users to create custom profile sites, express relationships with other users, and explore the resulting social graph [1], they combine previously available communication and self-representation functions, such as personal blogs, forums, and instant messaging with novel social functions. Also, they allow reaching new contacts. The user base of OSNs is no longer restricted to private end users and college communities [2] but extends to professionals while serving as collaboration tools [3].