Uh, they weren't "tasked with" it. You make it seem like they got this impossible assignment from somebody. They started the project themselves, then hyped it up before they had anything useable.
Nobody really contributes because it's a dead-end project, no matter how many contributors there are. As somebody else in this thread mentioned, "social" is not a software problem.
they didn't hype shit-- they put up a kickstarter (which is, indeed, for projects that "don't have anything usable" yet), and it got picked up by the NYT.
and diaspora is still one of the most contributed-to open source projects in the world. so no, it is not the case that "nobody really contributes"
Nobody really contributes because it's a dead-end project, no matter how many contributors there are. As somebody else in this thread mentioned, "social" is not a software problem.