The case for private social networks

The recent interest in the Facebook float is going to mean the worlds media fix their gaze upon the worlds largest and most open social network.

But what about the use of social networks beyond the open world? What about the plethora of closed or private social networks? Will these gain interest in the lime light of facebook? Take socialgo for example which takes its cue from facebook but provides a free and paid for private service. That enables one to monetize your revenue stream.