Our current mania is joining electronic discussion groups. Informal groups and ad hoc groups are too numerous to mention. But with respect to formal groups that announce their existence by having charters or announcing their meetings in newspapers, we are also joiners. A 1990 study managed to find some 23,000 formal organizations of various sorts, a large percentage of which had chapters or affiliates which, if counted separately, would have swelled that number enormously. These are organizations that people belonged to but did not work for, and the number counts such things as the Roman Catholic Church or the American Legion or the Boy Scouts only once.
Most groups have both an instrumental leader and an expressive leader.
Look at your list of groups again. Task groups such as work groups and groups which have to have decisions made generally give the instrumental leader more power. Authoritarian leaders focus on instrumental concerns, make decisions on their own, and demand strict compliance from subordinates. Democratic leaders tend to be more expressive and try to include everyone in the decision-making process. Once again consider the list of groups to which you belong.