Really, asking "what should replace Facebook" is putting things the wrong way around.
A more interesting way to ask the question is, "what did Facebook replace."
People used to build their own websites. People used to have blogs. People used USENET which was truly distributed and un-censorable.
Facebook and Google took the open internet and open standards and monetized and made everything crappy. Enough of that. Nothing should replace Facebook, it's done, stick a fork in it.
@mauve @hhardy01 I never use/used facebook, so when I meet people I just ask what they've been up to lately and you need to see people's faces when they see that you actually listen to their stories and do not answer "Oh, I saw it on FB"