Call it a “cryptocurrency” if that makes it sound sexy, but this is still centralized — it’s effectively the same as the (already existing) Messenger Payments.
That's an example of something Facebook has control over. If someone wants to fork it, they could, but it wouldn't affect the code Facebook is running. A blockchain would differ in the sense that the community/hashpower could decide to do things Facebook doesn't want to do at which point they would effectively lose control of the chain.
Open source makes sense for companies because they want to share the collective engineering efforts - because often times the code itself isn't the thing being monetized directly. In the case of Facebook it's not the code that is worth billions it's the data they horde. In the context of a blockchain that would mean sharing that data with everyone instead of hording it and acting as a middle-man for advertising, which is very much against the business interests of Facebook or any company with that model.
If Facebook’s developer teams have faster build times, they can create more horrible, unethical, revenue generating features per hour.
FB could have kept Buck for themselves but chose not to.
True. They might not. But maybe they only want to threaten (e.g., Google Fiber) that X, Y or Z might be possible?
The other reason for such things is talent. If you want to attract top talent you have to (R&B) toys for them to play with. On the other hand, to say, "We'll never release this so let's not put any effort into it" is the road to irrelevance.
The budget for this effort vs the cost of irrelevance make such project a solid investment. Pointless in terms of product but essential to the brand.
Because if it is not - it is simply a centralized database of payments. Like an SQL table of transactions. This has been a solved problem for decades. Visa and MC processing servers all use cryptography in many parts of the stack, and yet no one calls Visa a cryptocurrency because of that. This is why if you see anyone use the word "cryptocurrency" when in reality they talk about a legacy centralized (thus lacking all decentralizations perks) database - you know they are assuming you have no actual knowledge about the area and are trying to buzzword you.
Forget about centralized/decentralized. There is an ecosystem around existing cryptocurrencies. Wallets, exchanges, dapps, etc. All of it wouldn't work use they an SQL table of transactions.
The problem with centralisation is that it enables a kind of corruption: entities can engage in both financial censorship and arbitrary money printing.
That being said a cryptocurrency does not have to be decentralised.
However it is very important to understand the difference.
Today even decentralised cyptocurrencies depend on centralised-exchanges, and the consequence is that despite the constraints built into a blockchain algorithm are able to sell unlimited amount of the crypto to users without actually being in possession of the algorithm-limited crypto.
A centralized cryptocurrency is just digital currency. It may be cryptographically secured against unauthorized transfers/access, but if it doesn't employ some sort of game-theory based custodial sharing scheme which is intended to incentivize decentralization of control (successfully our not), it's not using the 'crypto' protection in the special sense that cryptocurrency implies.
If it's centralized there's no point in having it be a distributed consensus blockchain. The only reason to do so would be to play on people's ignorance for marketing reasons. That or maybe they really are ignorant themselves, but I doubt it.
Trust in it to maintain its value if it is a stable coin. Alternatively, trust it not to be hacked or inflated if it isn’t. (As well as trust it to maintain whatever monetary properties they advertise to give it value as money.