i think its about making it self validatable and auditable for his facebook credit system between his payment gate way and all his partners in the games industry(like zynga) and advertisers(like google)
As of now, that is the possible thing that facebook might get in cryptocurrency. The payment with the games and all tokens that the user will buy in order for their character in a game becomes powerful and higher level than other.
I also viewed a successful project weeks ago, their platform integrates social media sites in a payment system. Fast and reliable! I think it can be done also 100% if there is negotiation between facebook and ICO I've saw. I think also that facebook can be an advertiser of cryptocurrency and can be a system of transaction.