Thank you for the tl;dr. It makes sense that the forces applying to Facebook are largely economic ones. I wonder if someone has attempted a first-principles e

Thank you for the tl;dr. It makes sense that the forces applying to Facebook are largely economic ones. I wonder if someone has attempted a first-principles estimate of the cost per user of running a site with similar levels of interaction as Facebook. Ignoring costs for software development, media hosting, and moderation (none of which are trivial), would it be possible to support just basic text-based social networking with an income stream based solely on displaying unpersonalised ads (and without manipulating which content gets shown to users)? I'm imagining a federated social network, but maybe there are cost savings if you have effectively a monopoly and don't have to interoperate with other sites.