If you’ve started exploring crypto, you’ve probably noticed there isn’t just one “stablecoin” — there are dozens, with names like USDT, USDC, DAI, and many more. Why so many? And if they’re supposed to be “stable,” how can they fail? Both are great questions, and the answers tell you a lot about how to treat them carefully. Here’s the honest, plain-language version — with real examples of stablecoins that collapsed.
Quick recap: what a stablecoin is meant to do
A stablecoin is a crypto token designed to hold a steady value — usually pegged to one US dollar. The idea is to give you the speed and flexibility of crypto without the wild price swings. That “steady dollar” promise is what makes them so useful for trading, saving, and payments. But the promise is only as good as whatever is backing it — and that’s where the differences, and the dangers, come in.
Why are there so many?
Several reasons, all of which make sense once you see them:
Different companies want their own. A stablecoin is valuable infrastructure — whoever issues one earns interest on the reserves backing it and becomes central to how money moves in crypto. That’s a big incentive for exchanges and companies to launch their own.
Different designs. Stablecoins aren’t all built the same way. Some are backed by real dollars and assets held in reserve (like USDC and USDT); some are backed by other crypto held as collateral (like DAI); and some — the riskiest kind — tried to hold their peg purely through clever algorithms and trading incentives, with little or no real backing.
Different blockchains and uses. Some exist to serve a particular blockchain, exchange, or region. The result is a crowded field where most everyday activity flows through just a few big names, while many smaller ones come and go.
So how can a “stable” coin fail?
The key is that “stable” is a goal, not a guarantee. A stablecoin holds its value only as long as people believe it can be redeemed for what it claims to be worth. When that confidence cracks, people rush to sell or redeem at once — a classic bank run — and if the coin can’t meet that demand, it “depegs”: it falls below its supposed $1 value, sometimes to nearly nothing. The least-backed designs are the most fragile, because there’s little real value to fall back on when panic hits.
Real example: TerraUSD (UST) — the big one
The most catastrophic stablecoin failure in history was TerraUSD (UST) in May 2022. UST was an algorithmic stablecoin — it wasn’t backed by a vault of real dollars. Instead, it tried to hold its $1 peg through a complex relationship with a sister token called LUNA, where the system would create or destroy tokens to balance supply and demand.
A huge share of UST had been parked in a service offering an eye-catching yield of around 20% — an unsustainable lure that concentrated the risk. When large amounts were withdrawn and sold in a short window, UST lost its peg. That triggered a “death spiral”: as confidence collapsed, the mechanism flooded the market with LUNA, whose price crashed from tens of dollars to fractions of a cent within days. UST — once one of the largest stablecoins, worth tens of billions — fell to near zero. Enormous amounts of ordinary people’s money evaporated almost overnight.
Real example: Iron Finance (IRON)
A year earlier, in June 2021, the IRON stablecoin showed the same pattern on a smaller scale. It was only partially backed, relying in part on a companion token called TITAN. When large holders rushed to sell, panic spread, the backing proved insufficient, and TITAN collapsed essentially to zero — dragging IRON’s peg down with it in what was effectively one of crypto’s first big “bank runs.” It was an early warning that the same fragility would later destroy UST — a warning too few heeded.
What this means for you
The lesson isn’t “all stablecoins are scams” — the major asset-backed ones play a real, useful role. The lesson is that the word “stable” describes an intention, not a promise, and the design behind it matters enormously. Be especially wary of any stablecoin offering unusually high yields to hold it — that’s often a sign of exactly the fragile, under-backed design that has failed before. As always, understand what’s actually backing something before trusting it with your money. This is education, not financial advice.
Key takeaways
There are many stablecoins because issuing one is valuable and profitable, and because they’re built in different ways — backed by real dollars, by other crypto, or (riskiest) by algorithms alone. “Stable” is a goal, not a guarantee: a stablecoin holds its peg only while people trust it can be redeemed, and when that trust breaks, a bank-run-style collapse can make it “depeg” toward zero. The clearest cautionary tales are TerraUSD (UST), which wiped out tens of billions in 2022, and Iron Finance (IRON) in 2021 — both fragile, under-backed designs lured by unsustainable yields. Favour well-backed coins, and treat sky-high yields as a red flag. This is education, not financial advice.
New here? Start with what a stablecoin is and what a depeg is. For profiles of the two biggest, see Tether (USDT) and USD Coin (USDC).
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