In my very humble opinion, Facebook is a bit of a fad. I am on it, but don't use it much. Finding old friends from high school seems to me its principal value, and keeping in touch with friends in other parts of the nation/world is a useful secondary value.
Facebook could be quite useful in organizing movements, whether political or societal. I doubt its commercial benefits, though. Most people value privacy, and Facebook wants to feed on every digital connection of a person has to sell its ads. Yuck.
Re LinkedIn, I have no opinion as I am not a user.
Word of the Day
"Gratulation" - noun [$100] a T. S. Eliot word.
"Gratulate" - verb '$100] archaic.
Gratulation means 1. a feeling of joy; 2. the expression of joy.
Gratulate means 1. to hail with joy, express joy at; 2. to congratulate; 3. to express joy.
Sentence: [T. S. Eliot in "What is a Classic?"] "That is not in itself any more a matter of regret that it is for gratulation."