Will has some interesting points, my favorite being:
For example, if individuals’ decisions about consumption, savings, and debt are rooted in beliefs about their future incomes — a view I think most economists share — then it would seem that an economy-wide decline in personal consumption would indicate that a lot of individuals have more or less simultaneously revised their expectations about their future economic prospects. As far as I can tell no one has a theory of the events that predict revisions in an individual’s estimates of her lifetime income, much less a theory of how the perception of events predicts the magnitude of these revisions.Economists aren't trained in psychology. In fact, every time I tried to take a class outside my department, such as the few classes I took in sociology, I got a lot of strange looks from some of my professors.
As researchers of human action, economists are in desperate need of a good dose of psychology training. Perhaps the recent financial crisis, and the range of criticisms economists have received from it, might encourage this.