True, but when you find a Martian index fund that pays better than anything you can find on Earth, be sure to give me a call.
It would actually be a good sign at this point if investors lost interest in buying government debt (from the US or from other governments). Because then they would find something else to invest in... like maybe something that promised some gain, something that would put people to work and make use of idle capacity. The fact that everyone is anxious to hoard cash or cash equivalents, even at miserable interest rates, is an ominous sign: When deflation comes, hoarding cash for as long as you can is a paying proposition, and the economy spirals to a halt as everyone tries to wait through as much deflation as possible before buying anything.