"Power structure" is a term of convenience for a social organization in which control of (the actions of) the group's members is held by a comparatively tiny number of individuals. The intensity, or focus, of the power structure is roughly proportional to the degree by which the controlled outnumber the controller(s) multiplied by the tightness of control (degree of trust or coercion). The mechanisms by which such structures are maintained are sometimes called "power engines" , although this term is not (yet?) in wide usage.
Examples of power structures include governments, businesses, and churches; a power structure can also span several different organizations, sometimes including only some members of each.
Power structures are not inherently harmful or unethical. Even in the most egalitarian organizations there will usually be some form of power structure, as it is both a natural human tendency and a reasonable solution to the complex problem of making decisions in a group; indeed, probably any group of two or more people includes a power structure of some kind. Very intense power structures are often required in order to respond rapidly to emergency situations, e.g. in time of war.
The problem arises when the maintenance of the power structure begins to be the main reason for the group's existence, any original purpose being relegated to the level of being an excuse for the group's activities.
The phrase "social control structure" seems more descriptive and accurate; I may change the name of this article and the related power structure meme article. Alternative: "social control mechanism"... but I think I like "structure" better. --Woozle 07:26, 5 January 2007 (EST)