It seems to be a natural law that strength creates vulnerability. When an asteroid smacked the earth 65 million years ago, it was little rodents, not T. rex, that survived; and certainly the notion is woven through the events of September 11. Today, everyone knows that social capital—the relationships that bind communities—makes organizations strong. Well, you can guess where this is going.

A version of this article appeared in the December 2005 issue of Harvard Business Review.