Until recently I'd never really thought much about my social networks — the intricate web of friends, colleagues, and acquaintances around me. I always pretty much let these contacts happen by themselves, although I often marveled at the interconnected chain of events they spawned. As an example, consider this sequence of events. Not long ago, I was best man at the wedding of a college roommate of mine who married the daughter of the dean at a local university. I sat at the head table, and I hit it off with the bride's parents. A professor at the university subsequently mentioned to the dean that he needed his front fence restored; the dean gave him my phone number,
