A lot of important economic concepts have filtered into journalist accounts and even everyday conversation about our current finanacial crsis. Moral hazard, liquidity, credit contagion, deflation, etc. have all been used in various accounts that often demonstrate the old adage that "a little bit of knowledge is a dangerous thing" as much as the usefulness of these economic concepts to aid understanding.
To my mind, one of the most important economic concepts to be developed in the past decade is Bob Higgs's idea of "regime uncertainty" and the application to which he has put that concept to use to explain the deepth and length of the Great Depression. Given the earlier application, the relevance of the concept of "regime uncertainty" to our current situation should be evident.