One point is not clear to me and maybe someone can help me in understanding better. The classical Six degree experiment states that I can forward the message if I know the target person directly by name. If this is not the case, I can forward the message to someone I believe is closer to the target person. I always understood that there is a non null probability that the man in the middle can drop the message, either because he doesn't know the target or because he is not interested. In my view, this not null probability models my personal interest for the target person and how strong is our relationship. The closer I am, the smaller would be the probability of dropping the message.
On Facebook the fact that I am connected to someone doesn't necessary meaning that I would always send a message to him/her. Maybe, I missed this part in the paper and would love to understand whether the 4.3 degrees of separation is also modelling the fact that a message can be dropped with a non null probability.
Someone can help me in better understanding?