Agreed, why not build one that works??.
I believe there should be a positive side to every topic posted here rather than shaming a concept that can potentially be bigger than anyone can think of because of wrong execution.
A social network is not a bad idea, with the rate at which the Nigerian tech space and public accepts and try out new ideas, who says a community of Nigerians (and others) will not work. "Why not give it a shot?" thats what I thought about after reading your post and I am wiling to.
It can be an open source platform so other developers can chip in. We have Nairaland, naijapals, naijagist, LindaIkeji and several other blog/news community websites, we don't need another one, we need something different. I think the idea Linda pursued was to get her users to communicate better with each other because the comment section of every of her post is always flooded so I think she saw the potential to get more users by allowing free communication and even more to build a database of users which an be used for several purposes later on.
An idea popped into my head, not really a social network but something like a profile finder which can become social and interactive.