Right, but if you have patience I think its ok. Worst-case scenario I suppose would be the fund goes to near 0. You keep collecting a dividend and make your money back after ~13 years (not including inflation).
Of course, there's always the possibility the dividend decreases too (chance is probably small, with rates already low).
I think a lot of people would rather go for a higher/faster return in equities than bonds. Depends on your risk tolerance.