1. Facebook definitely doesn't have full and complete trust in their own systems, they are vulnerable to hacking, downtime, and mistakes just like any other ser

1. Facebook definitely doesn't have full and complete trust in their own systems, they are vulnerable to hacking, downtime, and mistakes just like any other service, and they know it. This is the same reason companies release messaging products with end to end encryption. 2. A traditional centralized database doesn't allow offline transactions with any degree of trust. I don't know if this is a problem they are solving, but in principle, something with a blockchain-like architecture makes it possible to provide cryptographic proof that you have the money and intend to transfer it without any server round trip and still be secure against many kinds of attacks.