I’m a fan of niche social networks, and I concede that Facebook apps can often benefit from having their own site. But I still think the newly launched neighborhood social network, Nextdoor, might have worked just as well as a Facebook app or group, or a Google+ Circle. It’s getting some attention today, due to its fairly broad launch (176 neighborhoods), intriguing digital/physical world viral recruiting scheme and leader Nirav Tolia, ex of Epinions and Shopping.com. Still, I like the chances of BranchOut, that’s launching a new premium service for recruiters atop its Facebook professional network app, better than those of Unthink, another anti-Facebook network. What do you think determines whether a social network should be standalone versus implemented as an app?