I think one of the main purposes for this coin is data gathering on users purchasing activity. Facebook makes its money through selling user data, and using it for behavioural profiling so they can predict (and influence) future behaviour. It's a very lucrative market, and is the basis of FBs profits.
There is no data that Facebook needs that is not already within his reach, and even if they release their coin, the people that will still be in their cryptocurrency community are those within its 2 billion users, which they already have their data through the Facebook account that they have all opened. I am just suspecting that one of the reason why they became keen about cryptocurrency suddenly is because of the accusation of government against them which resulted to the high charge that is being slammed against them, maybe they just want to create a decentralized system that will make their activities also open to the world rather than them getting slammed and accused of abusing their user’s privacy. We are the ones assuming they sell data because Mark denied it.
