I'm just about half way through a fascinating book, called "Linked", by Albert-Laszlo Barabasi. In it, he explores how networks grow: whether they be social networks, biological networks, the internet, or web sites.
One of his most fascinating points is that the study of an individual node - whether it be a cancer cell, an atom, a web site, or a person - is less important than understanding the connections between them. No matter how perfect the microscope (or how big the search engine), it is the interrelationships between the individual items that often determine behavior.
From a business or career perspective, we know this intuitively: it is our relationships with others that determine our success. This is true whether we are dealing with clients or suppliers (a relationship of trust will often close the deal) or with a prospective employer (who is referred through our network.)
Recently, I have started to use a web-based social-networking site, called LinkedIn. Not sure exactly where the ultimate benefit will come from, but strengthening my own connections (and using nifty software like this) can't be all that bad an investment.