This really speaks to how we should look at apps, specifically those based around social networks. Consider the analogy of an app vis à vis a roller disco. The roller disco was a fad, so why can't apps and their subsequent networks be "fads" too? Maybe that's the point: they're cool because they're relevant now. Maybe longevity isn't the goal. We should enjoy the ephemeral things (so later we can say "remember when...").