Fortune published a list of worst Business Decisions in 2008.
But I think dumbest of them is not listed in the main article.
Consumption beyond capacity by enormous amount of leveraging, greed, wrong housing market assumptions (nothing can go up indefinitely), wasting resources (4 SUV families). There are many dumb mistakes done by Americans (and so called Americanized world).
But the dumbest of all is not to work on Sustainable environment planning. We all know we can not meet our energy needs by the present technology. The best thing we can try is to create a massive research project (in the scale of Manhattan project) to invent new technologies to solve these problems. I hoped Obama will do that. But it seems Obama is more focused on creating jobs by unnecessary projects (building roads and highways, which I believe is not so urgent), bailing out(by taking new loans to make messier Federal Balance sheet)auto companies(which make crap vehicles) and stimulus packages(which may stimulate the wasteful over consumption habit of Americans and thus destroy a good habit(living frugally)recently developed within Americans).
This financial crisis can be a boon for us if we take lessons and change the way we do business. Investing in Sustainable science and engineering (geo-engineering), better accounting, better wealth distribution, minimizing wastages are few of the things we should focus now. Unfortunately we are not doing any of these and American well as world economy is becoming out of control day by day.