Facebook is a de-facto standard of communication. They have your info, you friends info - and you need FB to find and share with others.
The technology medium is completely irrelevant.
It's like saying 'hospitals are not important for saving lies, what matters the most are 'roads' because that's how sick people get around'.
My Space was never a communication mechanism, it was almost purely social, moreover, it didn't have broad appeal. My mother and grandmother never used MySpace - but they use Facebook.
Facebook has cross generational and cross cultural appeal, and has a 'global critical mass' making it the default platform for a lot of human communication.
I don't like Facebook at all, but they are here to stay for a while, until something else replaces it.