Mandating the purchasing of U.S. Treasuries?

This little gem of a piece discusses possible moves afoot within the government to force retirement account investments (401k's etc) into government treasuries. It sounds a bit off and more than a bit scary but there is a ring of truth and possibility to it. After all, if there are no buyers in the market for U.S. Treasuries, what happens to the government's ability to continue funding its deficit spending and interest payments on its debt? So, to prevent that, why not legislate (mandate) a buyer into existence? And, if this sounds far-fetched, as the author points out, Argentina has already embarked on this road...