It didn't take long after the first social graph was created to realize that your contacts define you as much or even more than your other indicators do. That's why so many companies are gunning for this information.
A quote I saw on the Internet long ago went, "You're the average of the five people spend the most time with". I used to interpret it only in its original, prescriptive sense: if you want to become a different person, make appropriate changes to your social life.
It took me way too long to realize it's even more applicable in the descriptive sense: the people you spend most of your time with are a good statistical predictor of who you are.
