Who do you know? Who do you trust? (external link)

Who keeps you sane? Who cleans off the dust?

To be sure, there is a lot of churn in human social networks even in the best of times. Several studies show we replace as much as half of our social network every five to seven years. Little wonder when research also shows only half of our friendships are mutual. That is, only half of those who we think are our friends feel the same way about us. It just normally takes us a while to figure that out.

The notion that only half of what I consider to be friendships are mutually considered as such rings true to me.