This paper proposes architectural styles for multi-agent systems (MAS) which adopt concepts from organization theory and strategic alliances. In particular, we discuss here the structure-in-5 and joint venture styles. These structures consist of actors who have goals to fulfill and social dependencies describing their obligations. They are represented in i*, a framework designed to model social and intentional primitives and formalized in Formal Tropos. Each proposed style is evaluated with respect to a set of agent software qualities, such as predictability, adaptability and openness. The styles are evaluated and contrasted with a software architecture for mobile robots, notably Lego Mindstorms