There’s nothing explicitly wrong with this. MBA’s aren’t intrinsically stupid, and excel is a reasonable tool for calculations. It’s just a pure functional language using geometric space instead of a namespace.
Yep - all the focus on the engineering specifics here seems to miss the sheer magnitude of the thing. Knight risked 4x their annual revenue in under an hour! You can get away with some incredibly crappy systems if you have final-line safeguards like "let's not risk all the money we've ever seen and more without asking a human".
The team of MBAs might screw up an Excel formula and lose money on a deal, but presumably if the math comes out to "let's pay $500 billion for Yahoo", somebody's going sanity-check that before they transfer the money.
I think companies have on occasion lost billions due to a glitch in a contract, sometimes due to delegating work to a novice who didn't fully understand it. And a contract is not totally unlike a program.
As a tool for rough approximations, spreadsheets are amazing. Beyond that though:
* Lack of unit (or any) testing
* Lack of good versioning practices and code review (e.g emailing around a sheet that's been doing the rounds for 15 years in various different guises and formats and has who knows what horrors lurking)
* Lack of typing (e.g doing a SUM across a dataset consisting of "3", $3, 3, "III", an emoji of the number 3, a jpeg screenshot of the number 3 - might not add up to 18)