I certainly don't know legal distinctions and what not
But at least in the United States the impression I've gotten is that Facebook is posed to decline.
I think they're in the "MySpace" realm of things. The undisputed current king, but also it's replacements out there are ready to take over.
Talk to a person under 30 and ask them what their thoughts are on Facebook. Most of them use it little to none at all
Unlike MySpace, Facebook has been ever evolving on multiple fronts - they're smart enough to know that the kids will always move to the next hot thing, so instead of chasing the zeitgeist they simply acquire it. Instagram and Whatsapp are the big ones, but they've bought dozens of other smaller apps. They're not just buying the apps and communities, they're buying the IP and the patents so that even if they are losing the battle for subscribers they're making licensing revenues on the back end.
They're also evolving the core app. No, 20 year olds aren't posting pictures of their lunch on Facebook any more, but they're the dominant force for community groups and increasingly for classified sales - FB Marketplace is becoming the global de facto. Loot, Kijiji, even Craigslist are losing share to it.
Facebook is a monster and will keep becoming bigger if it is left unchecked.
