  In this work we present an in-depth analysis of the user behaviors on
different Social Sharing systems. We consider three popular platforms, Flickr,
Delicious and StumbleUpon, and, by combining techniques from social network
analysis with techniques from semantic analysis, we characterize the tagging
behavior as well as the tendency to create friendship relationships of the
users of these platforms. The aim of our investigation is to see if (and how)
the features and goals of a given Social Sharing system reflect on the behavior
of its users and, moreover, if there exists a correlation between the social
and tagging behavior of the users. We report our findings in terms of the
characteristics of user profiles according to three different dimensions: (i)
intensity of user activities, (ii) tag-based characteristics of user profiles,
and (iii) semantic characteristics of user profiles.
