In the end I'm not sure that a real fully decentralised crypto is what the greater population wants or desires. There is just too much safety in being able to appeal to a central authority. Well, at least in the short to medium term, perhaps things are different in the far future!

Probably a meld of systems is what will be optimal for most people. But yes, it would be interesting if Facebook proves to be the gateway drug that gets people familiar with the wider ecosystem!