Treasuries No Longer Considered Risk Free

Marketwatch reports that the cost of credit default swaps for U.S. Treasuries is rising. The significance of this is that Treasuries are no longer considered to be 100% risk free. Usually, in finance classes, they use the yield of government securities as the risk free reference rate in for example the CAPM formula. But this presupposes that everyone perceives these securities as being risk free, something which is evidently no longer the case.

Personally, I don't think there is any risk of default for a government that issues debts in its own currency and has a fiat currency with a floating exchange rate, as it can always print whatever money it needs to pay. That might lead to a de facto default, as the real value that investors get back is lower, but it won't be the kind of formal default that credit default swaps protects you from. So the people buying these swaps are wasting their money for nothing. But that's their problem, and the point remains that Treasury yields thus contain a risk premium, and cannot be used as the risk free reference rate.