Herbert Simon is awesome.

Really, that's about all I want to say, although it's worth point out that he studied preferential attachment long before it was "discovered" (as some scientists might suggest) in the 1990s and he published a paper with amazingly modern views on complex systems and hierarchical organization in 1962. (Tip of the cap to Renaud Lambiotte for pointing this paper out to me.) Here is his wikipedia page.