Spontaneous production groups are thought to be less effective at larger scales. Lacking formal organization, larger groups spend too much time on communication. Vital resources are spent on keeping the group together, rather than on production. This becomes even more critical in online environments, where communication is reduced to rather narrow channels.
This is what the theory says. And it might even be true, if and only if, coordination is absent. Recent research indicates, however, that online production teams that aggregate spontaneously increase in efficiency as they become larger if they have good coordination mechanisms. Thus the Olson paradox needs to be qualified by introducing in the equation the presence and intensity of social structures.
A review of existing literature on this topic, especially in wiki environments.