Many covered call ETFs are vulnerable to market-wide sell-offs. If after the plunge, markets remain depressed for a bit longer than usual, then most income investors will see their cash flows shrink.

I've covered the iShares 20+ Year Treasury Bond Buywrite Strategy ETF (TLTW) several times in the past. I've been bearish, as the fund's above-average duration was excessively risky during a period of ...