Slate has a very nice piece on investors buying US Treasury bonds that yield negative interest rates! Now, why on earth would someone buy a bond with a negative interest rate? Though the answer is not complicated, it is more than a sentence explanation, so I will let you read it for yourself. Let me just say, inflation is involved.
For those of you not versed in corporate finance (or “core-fin,” as it’s known), the article provides a good summary of how debt markets work.