1) As the U.S. pays down the public debt, it raises important issues regarding benchmarks for risk-free assets, how the Federal Reserve conducts monetary policy, and what kinds of assets the government might accumulate.
2) The swap market has taken on some of the benchmark role of Treasuries, but it does not fully substitute as Treasuries are not subject to default risk. The Federal Reserve may need to use different tools for open market operations as Treasuries decline.
3) Accumulating assets raises questions about what types of investments the government should hold, like state/local bonds or private fixed income, and how to manage the investments independently and avoid conflicts of interest.