In a way, investors may see it as a safer bet today since prices reflect worst-case economic scenarios. What's more, such bonds, because they're riskier, yield relatively high returns of 7% to 9%. And at today's low-interest rates, it might come as a decent alternative.
Then again, the housing market is still a mess. And Europe's ongoing debt crisis has continued to rattle investors. Another crisis could certainly turn these bonds sour, but that's apparently the risk investors are willing to take.