facebook type products are an outlier. It did not require traditional sales and marketing in the true sense as it did one thing right : creating a tool for college kids like me where I felt like part of the community. The idea was brilliant to keep it to college campuses only. I remember looking at fb for the first time (circa 2004 when it was only on college campuses) and going "wow, they have listed my dorm name" and immediately felt a personal connection. genius!! And of course, the UI was far more engaging than the incumbents. So fb was selling itself but most products don't.
Facebook practically implemented a worse version of MySpace. The only problem with MySpace was security issues which I think ultimately killed it in the end.
