Very interesting article, but I belive one of the main assumpion is "Excel makes it easy to mess it up" because it's so easy to use that most non-technical people can use it, in a non-professional, careless way.
My question is : would the error in the model have been caught if the model would have been written in a more technical mean, say an R script ?
Excel does not give any feedback if the "error" is conceptual, but so it happens with more technical programming languages and environments. Excel puts out "errors" if you write a wrong formula, the equivalent of a syntax error for a programming language.
On the other hand, one would think the "on your face" presentation and ease of use makes it easy for other (non technical, but skilled in finance/math) people to review the numbers and calculations.
I agree with the author that I the fault lies in too many people trusting blindly the model, without reviewing the numbers/calculations, but I'm not sure Excel can be pointed out as the culprit.