Facebook and Mark Z. are now part of a very elite group. The heads of this group are central banks in American that would be the federal reserve. Which by the way is NOT federal and it does NOT have any reserves.
The federal reserve is the most threatened by cryptocurrencies. It will do everything in it's power to destroy cryptocurriencies, at least until they issue their own. They like the idea but they don't have control. That means all current forms will have to go.