This is an interesting development for sure and one that's well-worth being skeptical of for all the reasons you pointed out.
However please allow me to offer a rather significant and extremely positive benefit of what this FB crypto-token-thing will be that you overlooked. And it is this:
It will enable and allow more people across the planet (almost 2 BILLION use FB) to participate in this new way to exchange value, do business and improve their lives as a result. And there is NO telling just how much good can come from that many people contributing to the global economy. Especially for those people living in areas with limited local business opportunities. So even though the lion's share of the benefits will still be sucked up by Yuckerberg and FB corp, the benefits that users get by being able to transact globally in a fast efficient way is enormous. So to us crypto-savy people it's not an attractive project, but for the rest of the world's population which is not, the ramifications for the global peer to peer economy are profound!
You make an interesting point, but I dont know if you'll be able to exchange Suckerberg's coin with the rest... only time will tell, although I think that is pretty probable.
Thanks for contributing to the discussion.
Cheers