I'll start with the conclusion. I don't think flatcoins are a good idea.
The idea for flatcoins has been around for a while, but it got a wider airing when it popped up in a Coinbase marketing piece from earlier this year. Now, arch-crypto hater Nouriel Roubini has undergone a Damascene conversion and is about to introduce a crypto flatcoin, suggesting that these novel instruments are "the way forward."
What is a flatcoin?
If you own one dollar's worth of stablecoins or one dollar's worth of Wells Fargo deposits, both stay locked at $1 dollar indefinitely. A flatcoin, by contrast, slowly rises in value over time to compensate the holder for inflation. So if you own a single flatcoin worth $1 today, it will be worth $1.0001 tomorrow, and $1.0002 the next day, and so on. Twelve months later its value will have arrived at $1.05. This 5% appreciation protects you from 5% inflation, leaving your purchasing power unchanged.
Roubini and Coinbase are marketing flatcoins as a blockchain-specific thing, but there's no reason the concept couldn't by packaged up as a traditional financial product, one without a blockchain. Imagine a Wells Fargo account that holds 100 in Wells flatbalances which rise by 3-4% a year. Or imagine a flatnote, the issuer indexing the purchasing power of its paper banknotes to inflation by promising to buy them back at progressively higher prices.
Roubini stakes out a role for flatcoins as a potential "global means of payment." As far as monetary/payments technology goes, I disagree. I think flatcoins are an evolutionary dead-end.
One of the key features of money that makes it so popular is that it is directly fused to the dominant commercial language that we all use in our day-to-day economic lives.
What do I mean when I say commercial language? We converse and haggle with each other in terms of the dollar, we think and plan in terms of dollars, we dream in dollars, and we remember in dollars. Every facet of our day-to-day commercial lives revolves around this very basic measuring unit. (In Europe, the euro serves as the basis of Europe's commercial language, and in Japan it's the yen.)
The dollars that we own in our pockets (and in our bank accounts, as well as the stablecoins in our Metamask wallets) have been conveniently designed to be fully compatible with the dollar measuring unit that we refer to in language. That is, our media of exchange are pegged, or wed, to $1. For instance, if I've got to make a $1500 rent payment next week, I know that the 1500 units sitting in my bank checking account are a precise fit for meeting that obligation. I don't know the same about my other assets, say my S&P 500 ETF, my gold, my government bonds, or my dogecoins.
This standardization is a convenient feature. It takes a lot of hassle out of day-to-day commercial life. It means that when we buy things or make plans to buy things, it's not necessary to engage in constant translations between the dollar media in our pocket and the dollars in our speech and thoughts and plans. As Larry White once put it, harmonizing the unit we use in our speech with the units we transact with "economizes on the information necessary for the buyer's and the seller's economic calculation."
Since everyone tends to converge on these very useful standardized units for making payments (i.e. deposits, stablecoins, and banknotes), the markets for them have become highly developed and liquid. This only makes them more useful for payments, in effect locking in their dominance.
A flatcoin, by contrast, has been rendered incompatible with the dollars that we use in our speech. One unit might be worth 1.1145 times the dollars we use in our speech today, and 1.1147 tomorrow, and 1.1205 next month. This erases one of the most user-friendly features of money, its concordance with the commercial vernacular, alienating anyone who might use it for their day-to-day spending. Flatcoins will thus be less liquid than standardized 1:1 dollars, and this lack of liquidity will render them even less useful for making payments.
There's the secondary problem with flatcoins that stems from taxes. Since a flatcoin rises in value over time, all purchases made with flatcoins will generate a small taxable capital gain. This introduces an administrative burden which makes it even less likely that people will use flatcoins as an everyday medium of exchange.
This incongruity between linguistic dollars and flatcoins doesn't mean that people won't hold them. They might be useful as a type of long-term savings vehicle, much like how one might buy and hold a fixed income ETF. But unlike Nouriel Roubini, I don't think they are "the way forward" when it comes to acting as a medium of exchange. No one is going to be buying a coffee with a flatcoin.