For example, the General Social Survey requests respondents to name up to six individuals with whom they discuss “important matters.” The assumption is that people discuss matters that are important to them with people who are important to them … However, a recent study by Bearman and Parigi (2004) shows that when people are asked about the so-called “important matters” they are discussing, they respond with just about every topic imaginable, including many that most of us wouldn’t consider important at all. Even worse, some topics are discussed with family members, some with close friends, some with coworkers, and others with complete strangers. … Bearman and Parigi also find that some 20% of respondents name no one at all. One might assume that these individuals are “social isolates” — people with no one to talk to — yet nearly 40% of these isolates are married! It is possible that these findings reveal significant patterns of behavior in contemporary social life — perhaps many people, even married people, really do not have anyone to talk to, or anything important to talk about.
— from Structure and Dynamics of Networks