I don't think about what Facebook will do if they really create their own cryptocurrency.
some time ago Facebook has banned advertising related to cryptocurrencies on their platforms. but now they will create a cryptocurrency and join in it, what more drama will this big company do?
Facebook have many advantages if creating their own cryptocurrency. With large numbers of members, they can create their own marketplace and to transaction between members, should using facebook coin. Its great opportunity for facebook to create their own value beside as social media