Facebook is useful for keeping in contact with folks or if i run out of phone credit. I hate this whole like thing though, makes opinions seem cheap and worthless. its like you can sum up your outlook on life with a 'like' and a Facebook group (most of which have no discussion).
Ive never gotten Twitter, i dont care if celebrities are taking a poop, I've got better things to read about...
Ultimately though if people want to waste their lives they'll eventually get hit by a bus whilst tweeting away so really we all win!