A Friending Network works like this: A person has some number of fairly close friends that make up that person's social circle. Some of those friends are members of other social circles as well. When something fun or important occurs within a given social circle, the news moves across interconnected social circles like wildfire because the number of people transmitting the message goes up geometrically as the message propagates.
The physical method of message transmission can be by email, text-message, blog/journal entry, podcast, phone conversation, or even just plain old word of mouth.
Some net entities that rely (or relied) heavily on the friending network dynamic: