All that being said, bond ETFs do work as they should, and they can be a valuable component in any portfolio as long as investors understand the risks. Not all bonds and bond ETFs are created equal.

Meanwhile, bonds are as popular as ever. John Spence for The Wall Street Journal notes that bond ETFs accounted for 63 funds and $78 billion of the assets. Many expect this segment of the market to go through a major growth spurt now that PIMCO and others have entered.

For more stories on fixed income, visit our bond ETFs category.

Kevin Grewal contributed to this article.