As you point out, "social" can be done multiple ways: as a distraction or as a true value add. And I completely agree with you, it must be laid back and natural to be effective. That was our goal from the start for Socialbrowse: not to change your browsing behavior, but to enhance the way you already browse, and improve the sites you like to visit.
Socialbrowse is realtime, but doesn't require your attention. It's like a human powered RSS stream, so you can pick and choose which links you take or conversations you participate in. Or you can choose to ignore them completely if you're busy. We developed Socialbrowse to be there when you want it, but not to interfere when you don't. That's why it feels very non-intrusive, yet when you take it away, the web feels lonely again.