If Facebook is really building a blockchain, then I think that they are already digging their grave already, except maybe they will regulate the blockchain and any project that will want to come through their chain, because we can see what is happening to Ethereum right now.
If they dont regulate their blockchain, there are going to be lots of shit projects for sure. But, the way Im seeing it they are going to be regulating their blockchain. Facebook is a big company and I dont think they would like any of such things staining their name. Because, if they allow such things to happen then its going to make a lot of people hate them for it and that is going to cause them a bad business, which Im very sure they wouldnt like of course. But, we cant tell the future, its still a long way ahead
so till then we will get to know the full plans they have for this their Libra.
You should expect that project like Facebook own will really be of standard because they have had lots of experiences, managing up to 2 billion users and I believe that with their years of experience, they should have known better by now, which I believe they are also following the crypto space to see all the challenges that the technology has, which may be the reason why they also feel they could bring solution to the numerous problem and one of the solution would be to actually create some sort of regulation to limit the rate at which very terrible projects are being produced provided that people accept their system because they technology has not even been released and they are being welcomed already with lots of rejections which I think may make them change their mind.