South By North Strategies, Ltd.

Simon Johnson points out the a failure to raise the debt ceiling actually would make the size of the federal government larger relative to the overall economy.

The reason is simple: a government default would destroy the credit system as we know it. The fundamental benchmark interest rates in modern financial markets are the so-called “risk-free” rates on government bonds. Removing this pillar of the system – or creating a high degree of risk around US Treasuries – would disrupt many private contracts and all kinds of transactions.
…
In addition, many people and firms hold their “rainy day money” in the form of US Treasuries. The money-market funds that are perceived to be the safest, for example, are those that hold only US government debt. If the US government defaults, however, all of them will “break the buck,” meaning that they will be unable to maintain the principal value of the money that has been placed with them.
…
The result would be capital flight – but to where? Many banks would have a similar problem: a collapse in US Treasury prices (the counterpart of higher interest rates, as bond prices and interest rates move in opposite directions) would destroy their balance sheets.