Obviously, this is going to come to an end. Foreigners are not charitable organizations, and they're going to demand that we pay them back.
No single country owning large amounts of dollar-based investments is inclined to dump them abruptly; nobody aims to start a panic. But fears have begun to grow that one day a country may get spooked that another is about to dump its dollars--and that could trigger pre-emptive panic selling.
[Excerpt of an article by Peter S. Goodman, NY Times]