Economists predicted the likelihood of a global recession in 2007 at two in a billion - it was a "six sigma" event. This despite the fact that economics is essentially a history of recessions and depressions. It's not that everyone is stupid - it's that they come to worship the model more than what they're modeling. I would argue that this weakness can also afflict physicists.
I suspect that economists may be more susceptible to this pitfall then physicists. The theoretical underpinnings of economics, as you point out in your discussion of theoretically assumptions and practical results, are purely ideological. Economists whose work reflects a world view which is fundamentally optimistic about capitalism are more likely to insist that major recessions--events which cast doubt on capitalisms benevolent nature--are unlikely (if not impossible, the way many economists talked about a financial crisis in 2007).