Yield Has to Come from Somewhere
In traditional finance, yield comes from interest paid by borrowers or dividends paid from corporate earnings. The source is identifiable, and the sustainability is assessable. In DeFi, the sources of yield are more varied and sometimes obscured, which is where risk hides.
The fundamental question for any DeFi yield is: who is paying this return, and why? If you cannot answer that question clearly, you do not understand the risk you are taking.
Sustainable Yield Sources
Lending yields come from borrowers who pay interest to borrow assets. On platforms like Aave and Compound, the yield for lenders is funded by the interest rate borrowers pay. These yields fluctuate with demand for leverage. During bull markets, borrowing demand is high and lending yields increase. During bear markets, demand drops and yields compress. The risk is smart contract failure or borrower default (in undercollateralized lending).
Liquidity provision yields come from trading fees. When you deposit assets into an automated market maker (AMM) pool, traders who swap through your pool pay fees that accrue to liquidity providers. This yield is sustainable as long as trading volume persists. The risk is impermanent loss: if the price ratio of the two assets in your pool changes significantly, you end up with less value than if you had just held the assets separately.
Staking yields come from protocol inflation or transaction fees directed to stakers. Ethereum staking yields, for example, come from new ETH issuance and priority fees paid by users. These yields are sustainable as long as the protocol continues operating, though the yield rate varies with the total amount staked.
Unsustainable Yield Sources
Token emission yields are the most common source of unsustainably high DeFi returns. A protocol distributes its own governance token to users as an incentive. The "yield" is calculated based on the current market price of the emitted token. But as more tokens are distributed, supply increases, and the token price typically declines. The yield in dollar terms compresses even as the token emission rate stays constant. This is not really yield. It is subsidized marketing expense paid in a depreciating asset.
Ponzi-structured yields are the extreme case. The "returns" paid to existing depositors come directly from new deposits. As long as new capital keeps flowing in, existing users see returns. When inflows slow, the scheme collapses. These structures are not always immediately obvious, especially when wrapped in complex smart contract interactions.
Risk Assessment Framework
For any DeFi yield opportunity, assess five dimensions. Smart contract risk: has the code been audited, and by whom? Protocol risk: how long has the protocol been operating, and how much value has it secured without incident? Economic risk: is the yield source sustainable or dependent on token emissions? Liquidity risk: can you exit your position quickly if needed? And regulatory risk: is the protocol likely to face regulatory action?
A yield of 5% from a well-audited lending protocol with two years of operating history is a fundamentally different proposition than a yield of 50% from a new, unaudited protocol distributing its own token. The number alone tells you nothing about the risk.