If I was to give advice to anyone looking to build a social network right now, it would be pretty simple: go granular. Niche, even. The road to massive scale is closed, but another one has opened. A large percentage of a small base is still small. But a small percentage of a massive base is large.
M.G., this is exactly what we’re working on as we speak — addressing a specific job, for a specific consumer, with a value proposition that’s explicitly focused on users’ time: