You entirely missed the point. The community is on FB. They are not going to move, even if I build a much better site. I can't -- no one can, in fact -- offer them what FB does, which is that hub, plus connection to family and friends and job, including the very good chance of re-connecting with old friends, associates and classmates.
What they have is the public. Getting the public away from them is a pipe dream for anyone. Google couldn't do it, and Google+ is *far* better, technically speaking, then FB is.
It is simply glib to say "go build your optimum site" because to be optimum, the community would have to be there. And that is not going to happen no matter what you do.
As I already said, I can live with the down-side. What I can't do is replace with something of equal value.