It's getting problematic to hide this debt though because the last few years of deficits have been mostly financed by floating new tradable debt. The chart below shows publicly traded debt as a percent of total Federal debt. Prior to 2008 the ratio was about 50/50. Today Federal debt is nearly 70% publicly traded. This is concerning because it's obviously more difficult to control publicly traded debt.
The other issue is that as the Fed extends its maturities more and more, the maturity profile of the truly publicly floated debt becomes shorter and shorter. Short term funding is what causes banks to be susceptible to bank runs and was the primary point of failure for Bear and Lehman.