This is what Elon Musk told Twitter staff.
I think there’s this transformative opportunity in payments. And payments really are just the exchange of information. From an information standpoint, not a huge difference between, say, just sending a direct message and sending a payment. They are basically the same thing. In principle, you can use a direct messaging stack for payments. And so that’s definitely a direction we’re going to go in, enabling people on Twitter to be able to send money anywhere in the world instantly and in real time. We just want to make it as useful as possible.
And later offered more detail:
If you can simply have one balance on Twitter that can simply go positive or a negative, and when it goes positive, the interest rate is better than what you could receive elsewhere, and when it goes negative, the interest rate is lower than what you see elsewhere, now you have a much simpler system.
Then you attach a debit card to the Twitter account so that you have backward compatibility into the payments system because not everyone will accept Twitter. So if they have above a certain balance, you automatically send people a debit card. You want backward compatibility to the existing financial infrastructure.
In the US, there’s still a small number of checks that are used. So if your landlord is demanding that you send a check, you have to have some non-zero number of checks. Then we would send a small number of checks to those that need to have checks. Then you add automatic payment. Then over time, you basically address what are all the things that you’d want from a finance standpoint. And if you address all things that you want from a finance standpoint, then we will be the people’s financial institution.
From Everything Elon Musk told Twitter employees in his first company meeting – The Verge:
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