This chapter explores a case study in which the arrival of new participants in a long-lived association led to unforeseen and deleterious processes and implications in the dynamics of daily group life. The case study is important for at least two reasons, one descriptive and the other analytical. Firstly, it shows how the paradox of growing civic participation under conditions of increasing molecularisation not only covers the third sector as a whole but also applies to individual organisations, whose associative processes sometimes produce equally and perhaps more significant dissociative effects. And secondly, it provides an opportunity to investigate and account for this paradox—to try to identify the conditions that cause new forms of civic participation to renew associative processes, nurturing their institutionalisation rather than contributing to their deterioration. The empirical analysis derived from this case study shows the importance of associative styles in helping to shape the situated outcomes resulting from the spread of the so-called new forms of participation. In particular, this chapter outlines some of the most consolidated associative styles in the Italian third sector, including militancy and proactive citizenship.