That being said, a meaningful portion of the premise is doubtful:
"In order to realize its hundred-billion-dollar dreams, Facebook needs to forever dominate all of the world’s social interactions"
Not really. In order to realize it's hundred-billion-dollar dreams, Facebook needs to figure out
a. how to make more commerce happen (Eg gifts)
b. how to make more ads happen (As they're working on) or
c. how to make a kind of ad that converts at a massively higher rate, (such that ceteris paribus, their ad inventory climbs in value)
Dominating all the worlds social interactions, while a nice goal, is hardly necessary, and if that was the standard Facebook was judging itself against, they're likely being set up to fail fail. For example - email in the work context is a social interaction (and a large and high value one at that). What are the chances those sorts of interactions (Where privacy/security/proprietary data are concerned) ever happen on Facebook?
Physical postal addresses (and address books, if you insist).
Telephone numbers (and address books, if you insist).