  A challenging problem in the social sciences is the characterization of the
formation of ``social capital''. It is believed that societies with more social
capital are more democratic and economically developed than societies with
little social capital. However, social capital is a concept hard to quantify
and measure in a ``real-word'' context. Here, we take advantage of an existing
"web of trust'' between users of the "Pretty-Good-Privacy" (PGP) encryption
algorithm, which is used in digital communication to ``sign'' documents so that
the recipient knows for sure who the author is. Our analysis reveals the
coexistence in the web of trust of a macro scale-free structure with micro
strongly-connected cells in a complex network. We also show that when this
network is intentionally attacked the scale-free structure rapidly
disintegrates and that the resulting network is partitioned into a large number
of small strongly-connected cells that are resilient to the intentional attack.
