http://knowledge.wharton.upenn.edu/article.cfm?articleid=2170

Sociometric opinion leaders may or may not have the personality characteristics that first come to mind when one thinks of “leader.” In fact, they may be reserved and, as the above article says, “self-effacing.” But when push comes to shove, they are the people whose opinions are valued. They are sought out for their expertise, imitated and followed. They are often the first to adopt new trends and are apt to seek the opinions of others. They are leaders and followers.