Yes, the future deficits are worrisome says Jim Hamilton at Econobrowser. He's responding to a series of articles and blog posts by Paul Krugman--most recently this column on "the phantom menace"; see also this blog post on invisible bond vigilantes--arguing that the dangers of public borrowing are being exaggerated.

It's an important discussion and you should go to the sources. But here's a summary. Krugman stresses two main points. First, to make fiscal policy sustainable, you don't need to reduce the ratio of debt to output, you just need to stabilise it--and there is no compelling reason why you should aim to stabilise it at current levels, rather than at the higher levels which several more years of big deficits will cause. Countries like Belgium and Italy have much higher debt ratios than the US. So what's the problem?  Second, economic growth makes deficits and additional debt easily affordable, so long as interest rates are low enough in relation to the growth rate to keep a lid on debt-service costs. Interest rates are (very) low at the moment, so what's the problem?  More here.