This article aims to identify key elements explaining success of social casual games in the Facebook context. We argue that game success originates from the relationship between psychological needs of users and the social situation provided by the virtual environment (Facebook). In particular, we will analyze Facebook's ‘social casual games' using Murray's categories. This approach will help us to demonstrate that the success of social casual games in Facebook is due in part to the same element that acts as lever for general games, and in part to Facebook's social aspect, which acts as an amplifier. For this reason this paper will first define what a ‘social casual game' is, then it will use Murray's categories to underline several characteristics of social casual games in Facebook, and finally it will use a pilot study carried out by the authors in order to understand what motivates people to play in the Facebook context.