You mean WeChat.

People who are unfamiliar with WeChat Pay in China, are underestimating the potential for the FB cryptocurrency. The integration of social media and payments by WeChat strongly facilitated consumer adoption of their payment service. Everyone already had phones, everyone had WeChat installed on their phones. When payment services later became available through WeChat, there was a minuscule barrier for customer adoption. As people started using WeChat Pay they quickly found it more convenient for physical and online payments, money transfer between friends, and financial management. Next services like taxi hailing + payment became integrated into the WeChat app, increasing the convenience. The combination of convenience, preinstallation in the dominant social application, and low barrier to entry was a killer combination. In my estimation it turned out to be a stronger combination than Alipay, which started out as a payment service integrated with TaoBao (comparable to the Ebay / Paypal).

Since Facebook has a dominant social app and messaging app position worldwide, their payments service will have worldwide penetration from day one. Since Facebook can do software, the service interface will be more convenient and user friendly that existing services in the first world, and infinitely more so elsewhere. Money can be made here and evidence suggests people want to adopt when there is a no effort road to adoption. There are vested interests to deal with and satisfy on the road to market penetration, existing market players and governments, but American entrepreneurs like Gates and Jobs were able to overcome vested interests in their time and I suspect Mark is equally resourceful when he wants to be.