Wow, Excel really sucks. To be fair, that isn't just Excel, but any spreadsheet that's used to make decisions in business (or government) and hasn't had proper auditing or checking. Spreadsheets are amazingly powerful and useful, and so ubiquitous that Microsoft gave up on a separate BI tool and built one into Excel.
I ran across this story on a serious Excel issue that cost a lot of money in the London Whale case. There are a lot of comments with the post as well as a discussion on Hacker News as well. I also found this piece on the amount of spreadsheet errors that exist in the world, based on a number of studies. It's dry reading, and also a scary view of the world of spreadsheets.
As I read through the thoughts and posts, I'm somewhat stunned that we don't have many, many more business problems because of a spreadsheet being used as an application without any auditing. Perhaps we actually do and just don't know about it. Perhaps the reason you didn't get a bonus last year at your company was because of a spreadsheet error. There could have been either an error that caused a poor business decision, or one that incorrectly calculated bonus payouts.
It's a mess, and I honestly don't know what to do. A more rigid structure in building applications that are checked, rechecked, audited that can prevent the miscopying of formulas is a great idea, but in the real world, we know it takes too long. Perhaps more time is a good thing and businesses should slow down, especially financial businesses, but I can't see that happening either. Perhaps we need more tools that handle precedents and dependents. Personally, I'd also like to see some VCS hooks built into Excel that would help with controlling the code and auditing changes.
The entire process of building applications with spreadsheets reminds me of a race to the bottom, where companies take more and more shortcuts and chances, just because they think other companies are doing the same thing. Ultimately I don't think we can fix this, but we can try to make a difference by producing software quicker, and pointing out the errors in spreadsheets that become too important. We can meet somewhere in the middle between a full application development lifecycle and total ad hoc spreadsheet based tracking and processes.