I also think that this FB clone will fail.
And so far i fail to see the killer feature, i dont the circle UI be such convincing enough, in order to justify all that hussle as JBF described it.
I remember that ppl refused to do the step from the mediocre high5 to the far superior FB because of that.
FB with its pokes and likes has infiltrated everywhere, the tweeter managed to challenge it by offering smth else, but not to replace it.
Google+ will try to replace and therefore it will fail, it came far too late and it is not much more advanced, just different. FB latest update already brought groups and they can anytime update those groups, already formed and complete with a circle like UI.
The army of Androids could help though, but it doesnt seem impressive enough and the circles there are absent.
Maybe if they offer skype-like quality of video calls and significally superior UI, as long as free access from the networks, like the FB does, they would have a small chance...