For everyone to have the opportunity to be involved in a given group and to participate in its activities the structure must be explicit, not implicit. The rules of decision-making must be open and available to everyone, and this can happen only if they are formalized. This is not to say that formalization of a structure of a group will destroy the informal structure. It usually doesn't. But it does hinder the informal structure from having predominant control and make available some means of attacking it if the people involved are not at least responsible to the needs of the group at large.
This means that to strive for a structureless group is as useful, and as deceptive, as to aim at an "objective" news story, "value-free" social science, or a "free" economy. A "laissez faire" group is about as realistic as a "laissez faire" society; the idea becomes a smokescreen for the strong or the lucky to establish unquestioned hegemony over others. This hegemony can be so easily established because the idea of "structurelessness" does not prevent the formation of informal structures, only formal ones. Similarly "laissez faire" philosophy did not prevent the economically powerful from establishing control over wages, prices, and distribution of goods; it only prevented the government from doing so. Thus structurelessness becomes a way of masking power