Measuring the volume of information that the users, deliberately or not, leave on-line is an impossible mission. The vast majority of the actions performed by the users enclose more information than what the users themselves think they are producing.
To shed light on this truth, the talk will start with different examples of implicit information, namely traces that are often hidden inside other explicit feedbacks, or directly detectable by the users' actions. The focus will then move to browsing behavior analysis, including approaches to get a deeper understanding of the users, in particular cold-start situations. The talk will conclude showing how to follow these users traces to obtain reliable knowledge about the content consumed by the end-users.