With economic woes threatening to push the economy into a rare bout of prolonged deflation, investors in TIPS–Treasury Inflation-Protected Securities–and I-Bonds have cause to be concerned. These bonds, issued by the U.S. federal government, are designed to give investors protection against rising prices, which can eat away at the purchasing power of interest payments. But with plummeting energy prices dragging down the Consumer Price Index, these investments’ special safety mechanisms can actually work against investors.