A method and system for assessing a user reputation and/or a content reliability on contents sharing web sites is provided. In one embodiment, the method includes defining a networked association between users based on social activity information related to the users' social activities on a contents sharing web site, the users' social activities including social activities between the users and/or social activities of the users on the contents sharing web site; obtaining a link relation for at least one of the users based on the networked association; and computing a user reputation for the at least one of the users based on the link relation. The method may further include computing a content reliability of the at least one user-created contents based on the computed user reputation.