Are there universal circumstances that lead to failures such as Enron and Long-Term Capital Management? This author argues that two conditions are almost always present: something akin to a sure bet, where a value proposition or trade appears virtually irresistible, and a critical error of judgment as to a firm's market impact, that error of judgement often leads managers to overestimate the degree of portfolio insurance they thought they had. In short, they failed to appreciate their own impact on market liquidity, should they need to square their books. Without denying that "bad investments" are necessary pre-conditions to a crisis, the author suggests that the public focus on bad investments or questionable accounting is only part of the problem. The other is a failure to understand the dynamics of a trade, throughout the full spectrum of possible outcomes.