It's the friendship paradox. Studies of offline social networks show a trend very similar to the online kind - we each have fewer friends than most of our friends have, the same as almost everyone we know.
An analysis of Facebook’s active users, 721 million people then, and its 69 billion interweaving friendships, found that a user’s friend count was less than the average friend count of his or her friends 93 percent of the time. Averaged across Facebook as a whole, users had an average of 190 friends, while their friends averaged 635 friends of their own.
What gives? Is that 'jobs saved or gained' and 'every tax dollar you spend is an investment that yields $1.40 to society' fuzzy math? No, it's simple arithmetic, though counterintuitive, but it can explain away the mystery of one of life's little mysteries.
The math magic is really just the way averages are portrayed. If I teach a seminar on science writing to 90 people in one class and 10 in another, my average is 50, but that isn't telling anyone a lot of about the actual classes. Friends have more friends than individuals do for the same reason.
Prof. Steven Strogatz of Cornell, writing in the New York Times, has a fun analysis: Friends You Can Count On
