Thought-provoking post on why Facebook, like all networks, is doomed to fade (was their recent drop in US and Canadian traffic the first step?):
Networks have more than a utility based on connections; they also have a shelf life. Our fundamental insight is all those connections can grow or diminish in value at once — based on the context of the network vs. its competitors. Yes, networks rise in value and build gravity to draw masses to their center. But like a planet teeming with life that begins to pollute its own atmosphere, eventually all users long for a fresh start.
Nevertheless, Facebook seem to be continuing to try and innovate: they have a photo-sharing app in the works, and even I was floored by their COO Sheryl Sandberg recently!
One Size Fits One 