Agreed. But lending to a riskier counterparty for 24 hours is usually going to command a lower risk premium than lending to anybody, even the US government, for

Agreed. But lending to a riskier counterparty for 24 hours is usually going to command a lower risk premium than lending to anybody, even the US government, for 10 years. That's the essence of the story here. You make a valid point though: until now it has been riskier even to lend for 24 hours to a bank because of the binary nature in which banks go bust: they're solvent until they're not, and the run can happen in an event-wise, unpredictable fashion. The real story then is that even taking into account this high banking-sector risk, the US government is now riskier. But this has much more to do with the unlimited printing of debt (the real story) than the IRS market swap spread, and my wider point is that daily margining has been ignored by many of the people (here and in the financial markets chatter) who are talking up this issue as some kind of rubicon moment. This has been in the making for years and the slow grind below zero is not something that should be seen as extraordinary, nor, given the aforementioned slow grind lower, should it come as any surprise that it can go negative.