If you surveyed people forty years ago, at the dawn of the internet, and asked them, "If you could connect a billion people with a piece of software, what could you enable them to do?" I'll bet you they would sound pretty ambitious and optimistic. They'd probably talk about world peace, global education, or solving tough problems in the environment. Telling the world you like Pepsi or giving a thumbs up to photos of the high school friends you haven't seen, don't really care about, and would otherwise never really thought of again would have probably been pretty far down the list.
( Source: This Is Going To Be Big | The Underwhelmingness of Facebook )
A good read on the value of Facebook.
I initially took this as a dig at the founders and operators of Facebook but the more I read this passage, the more I think it's geared towards the users.