What I was trying to convey was that a social network doesn't necessarily need to move the mountains of money that Facebook does. Diaspora* is an example of a free open source social network platform. Of course it still cost people a lot of time and money to build and host it, but nowhere near Facebook levels.

I also think the business model of running specifically a social network as a profitable business is likely to lead to "perverse incentives". Making a profit isn't necessarily opposed to helping people connect (e.g. OKCupid's business model of being free to all but selling advantages to power users), but it takes both the willingness to align your business model with your users' interests and the fortitude to stick to that approach even though other approaches could be more profitable.

One is a great place do be if it wasn't for all piles of steaming crap left around by irresponsible users.

The other is somewhere to exercise your dog