What this really does is “vet” the quality of links for Google within your social circle. Although there will be privacy concerns, I’m generally for it, actually. It is 100% opt-in.
I’m far from alone in saying that tactics like this could go a long way to diluting the black hat SEO influences that have been steadily poisoning search results with junk (“answers” sites and link stuffing, anyone?). Check out “Trusted Sources” thoughts in the article Will SEO Kill Search Engines or Will Search Engines Kills SEO?.
Nice to see it getting some traction.