I have a question for those who know better than me: What's the critical mass for a social network to be self-sustaining? Even if 1 million people used Color,

I have a question for those who know better than me: What's the critical mass for a social network to be self-sustaining? Even if 1 million people used Color, I could those users concentrated in a few cities. Not only does the app require a vibrant, heavily active user-base that's willing to sacrifice their privacy, but it seems only useful in areas where the population density is relatively high. A 100 foot radius is an extremely limited area. Furthermore, what's the point of seeing other people's pictures? I find very little "social" value in the realm of location sharing. I, for one, would not approach anybody that I see in my stream. Even in Twitter, I use location based services little to never. What am I missing out on? Someone please tell me that I am wrong, but the success of Color requires far too many assumptions and is riding on a trivial purpose. I don't see how it deserves $41 million in funding... Color would work as a novel Facebook feature but, on its own, seems pointless.