Shorter-term funds haven't been hit as hard, but even the broad-based Vanguard Total Bond Market ETF has fallen 3% over the past few months, as has the inflation-protected iShares TIPS Bond ETF . Yet in recent months, even as the Dow Jones Industrials have kept pushing higher, bond investors have seen firsthand just how disastrous it can be when there are massive fluctuations in a rising-rate environment. The iShares 20+ Year Treasury ETF has lost more than 13% of its value since the end of January, illustrating the danger of long-term bond funds in a rate environment like this.