number of components exceeds what could reasonably be fully interconnected
> hierarchicality
> > modules (object oriented programming)

arguments regarding the prevalence and necessity of hierarchy/modularity in nature:
Koestler, Athur (1973), "The tree and the candle", in Gray, William & Rizzo, Nicholas D., Unity Through Diversity: A Festschrift for Ludwig von Bertalanffy, New York: Gordon and Breach, pp. 287-314


It has been proposed that perception itself is a process of hierarchical decomposition (Leyton 1992), and that phenomena which are not essentially hierarchical in nature may not even be "theoretically intelligible" to the human mind (McGinn 1994,Simon 1996).

Practical applications of functional decomposition are found in Bayesian networks, structural equation modeling, linear systems, and database systems.

http://en.wikipedia.org/wiki/Functional_decomposition