Canceling the debt of the developing world is possible if all debt is canceled. In light of the recent economic crises throughout the world, all debt should be wiped clean with all countries having a clean slate. This would allow all countries to prosper without further suffering, especially developing nations.
The cancellation of debt for poor countries is entirely bearable. In many cases, the debtor nations have already paid back many times what they paid due to high interest rates; one could "pay off" the debt merely by declaring, in hindsight, that a lower interest rate is justifiable. In any case, it is clearly bearable, just as it is bearable for a man or woman who owns a house or car to give a few pennies to a beggar. The amount of money it would take to dissolve all 3rd world debt is insignificant compared to the size of the economies of rich countries, and would have many humanitarian benefits.