Private social networks - a growing trend or a niche?

When you observe something once it is an outlier, twice is lucky and three is a trend.

Social networks by their very nature are public and open.  Venture money and marketing like open, big and public as the numbers tend to add up.  With 10% of the worlds population now on one big network (and the same 10% on numerous other small ones) what do the other 90% do, maybe they go for niche private social networks oriented to their specific need?

Here are several that need to be categorized and put into a fancy four quadrant matrix (enterprise, family, collaboration, messaging) Flink12, SocialGo, ChatterTree, Yammer,  Beluga (Facebook) and Disco (Google) and I am yet to be convinced if privacy is the issue that will drive niche or actually a desire to find value for the individuals!

An issue for those who join the small ones is that they may miss out on the ease of connection and have their data in a stove pipe that prevents it creating value (but that may be the aim).

Anyway – is this a suitable topic for a mashupevent* ?