Cryptocurrency is about trust. With most cryptocurrency you don't have to trust anyone: You have to trust the blockchain implementation, and whatever problem is required in order to not cheat at acquiring it. You don't trust a bank, government, corporation, or person to do the right thing. Depending on the currency you might trust that your transactions are anonymous(or at least difficult to trace to you).
Facebook? Can you think of a less trustworthy entity on the planet to trust?