As usual, Krugman is right.

And I am so tired of people whose eyes glaze over when they hear the word "exponent" tell me that we should jump off a cliff because they've done the math and I supposedly haven't and the Nobel-winning economist who's been consistently right doesn't.

http://www.nytimes.com/2012/01/02/opinion/krugman-nobody-understands-debt.html?_r=1

Excerpts:

First, families have to pay back their debt. Governments don’t — all they need to do is ensure that debt grows more slowly than their tax base. The debt from World War II was never repaid; it just became increasingly irrelevant as the U.S. economy grew, and with it the income subject to taxation.

Second — and this is the point almost nobody seems to get — an over-borrowed family owes money to someone else; U.S. debt is, to a large extent, money we owe to ourselves.

This was clearly true of the debt incurred to win World War II. Taxpayers were on the hook for a debt that was significantly bigger, as a percentage of G.D.P., than debt today; but that debt was also owned by taxpayers, such as all the people who bought savings bonds. So the debt didn’t make postwar America poorer. In particular, the debt didn’t prevent the postwar generation from experiencing the biggest rise in incomes and living standards in our nation’s history.

...every dollar’s worth of foreign claims on America is matched by 89 cents’ worth of U.S. claims on foreigners. And because foreigners tend to put their U.S. investments into safe, low-yield assets, America actually earns more from its assets abroad than it pays to foreign investors.

...nations with stable, responsible governments — that is, governments that are willing to impose modestly higher taxes when the situation warrants it — have historically been able to live with much higher levels of debt than today’s conventional wisdom would lead you to believe. Britain, in particular, has had debt exceeding 100 percent of G.D.P. for 81 of the last 170 years. When Keynes was writing about the need to spend your way out of a depression, Britain was deeper in debt than any advanced nation today, with the exception of Japan.

Of course, America, with its rabidly antitax conservative movement, may not have a government that is responsible in this sense. But in that case the fault lies not in our debt, but in ourselves.