Social networking insights from Paul Adams; his book Grouped is high on my current recommended-reading list
When telling this story, I usually gloss over an important related fact. Although the average Facebook user is only communicating directly with four of their 130 friends in any given week, they are consuming content from a much larger number of those people. After all, over 50% of active Facebook users come back every day. If you include consuming updates from people as communication, then people are interacting with many more than four, but much of the communication is asymmetrical in nature. I may not communicate directly with you, but I do keep up with what’s going on in your life.