Facebook's character fundamentally changes - again.
As it grows, I'm sure inertia will continue to slow it down, but that willingness for reinvention seems like quite a powerful property.
(Another current book – Antifragile (http://amzn.to/2nr15ST) – discusses systems that benefit from randomness and volatility. I wonder if the willingness for reinvention allows for a kind of anti-fragile generational selection to work: instead of waiting for selective forces to birth a different and new stronger generation, you transform yourself (or your company) to _become_ that new generation, allowing you to directly benefit from selective pressures. It's tough to do, psychologically and culturally, and the willingness to do so seems an extremely valuable quality to cultivate.)
Facebook measures and adapts to user engagement. When something spurs a loss of engagement eventually it disappears. In the social space, other tech companies struggle just getting a few new things shipped and then bail when they don't look like they are working out.
It is in Facebook's best interest to see Snapchat fail. The next big thing that comes around, it will be a lot easier for Facebook to buy early on.
On another note, if Instagram, Messenger, Whatsapp, and Facebook all start looking like the same app, it gives Facebook a particularly powerful platform. Everything could end up being rolled up in to a single app in the future -- or a new device.