I disagree with this premise. IMHO, it is much simpler: we as individuals lived beyond our means for 20+ years by borrowing money against our houses and against our personal word (e.g. credit cards). We as governments lived beyond our means in terms of direct spending as well future spending promises (e.g. promising retirement/pension/medical benefits that are funded by borrowing or not funded at all). Big companies also promised retirement (pension) benefits that assumed a continuing growth of the investments that backed the pensions - that didn't work out so well.
"But why now, when it hasn't in the past?"
In the past, we relied on general growth exceeding our indebtedness, "growing" our way out of our debt. This is a game that cannot go on forever... and the longer it goes on, the worse the crash will be at the end. Right now, it is looking pretty tough.
In short, we lived beyond our means for 20+ years. We will have to live "below our means" for a substantial number of years to balance our past spending against our current and future incomes... and that assumes we have the will to make the hard decisions to truly reduce our spending rather than claiming to reduce spending, but the "reductions" are 2/5/10 years in the future.
A big part of living "below our means" is buying less, paying down our debt, which means lower demand and thus lower job levels.