Okay, this is nothing new but that doesn't mean that it makes it any less worrisome for me.
Blockchain is no doubt immutable (and thus the craze for privacy coins) and if they have everything on it, then all then all of it is available to anybody who can get a node access. With facebook this becomes even more dangerous because they will and have commercialized every aspect of that information and would sell it to the highest bidder regardless any and all consequence except money.
I have always believed that very strategically placed individuals in and out of the government are the creators fake news and the system is a mere distributor of it. Although for the last decade it does seem that this task has been delegated to Facebook.