Amazon has already been working on managed blockchain technology for some time, now marketed to Amazon Web Services subscribers.

So I am sure they must have thought long and hard about implementing it for their own financial purposes, if not actually already tried it.

They probably already have much better in-house expertise than Facebook.

Maybe that is the reason they are holding back; they will know that it is not as easy to make money using a closed blockchain than is often promoted by companies and individuals looking to make profit in that area.

Many companies have dabbled in it, and been burned, I think many more than can admit it, which masks the problem.

The advantages of crypto that we see in open permissionless systems appear to be mostly lost, or outweighed by the cost of implementation of closed / managed blockchain solutions.