Earlier quoted context omitted.
In some models, sure, but is that true in Facebook's? Does anything go beyond one degree? I can't think of anything, really. If X and Y becomes friends, X's friends and Y's friends see it in their feed ("inbox"), but nobody else. Same goes for tagging someone in a photo, etc.
Ad targeting, what's hot in your network, friend recommenders, etc. are all essentially ranking problems. They're moving more in that direction, definitely.
Word. True. I knew there was something I wasn't thinking of.