Tipping points ?

As usual, I've been sifting through reader comments on news articles related to health care reform, which led me to this question: At what dollar point does government debt and deficit spending become unsustainable ? We spent years watching Bush/Cheney try to conceal the red ink with accounting gimmicks, flush billions of dollars down ratholes, and run up what seemed like huge amounts of debt. Every time a new record for reckless spending was reported, the response among conservatives was a collective yawn, with possibly a few comments justifying or rationalizing the situation.

So I need clarification. Where was the tipping point ? Little Dick Cheney once alleged that budget deficits don't matter, so when did things change ? Is $ 1,000,000,000,000.99 okay, but $ 1,000,000,000,001 too much ? We need to get this nailed down for future reference, to keep confusion at a minimum.

Added 10:14 am, same day:

This is on a somewhat different subject, but I had to work it in someplace. At some point, we're going to need to have sanity restored. Maybe I'm wrong, but for some reason, right-wing conspiracy theorists worry me more than the Obama administration. Eventually, Republicans will be running the show again, and nothing I'm seeing these days makes that prospect even remotely reassuring. Obama Derangement Disorder results in O.D.D. behavior, and these motherfuckers are crazier than I thought.