I don't see what problem Facebook thinks it's solving here. To me it looks like Facebook just sees companies like PayPal, Apple and to a lesser extent Google making a lot of money by piggybacking on top of the existing credit card, ACH and/or SWIFT systems and they want in. It's still a centralized solution, relying on technology we've all had indirect access to (through our banks and our credit/debit cards) for decades. When PayPal came along, they at least made the leap from having to go to the bank or a Western Union to wire money, to being able to just email money to someone. I don't see any similar leap with any of the solutions that have come along since PayPal with the possible exception of NFC payments with Google Wallet and Apple Pay.

A threat to Bitcoin? No, just someone else trying to capitalize on PayPal's business model.