As someone who sees a lot of financial spreadsheets, I'm often pretty alarmed at the bodges, hacks and general un-auditable-ness that seems commonplace.
These are multi-megabyte, massively-linked and inter-linked tomes that spit out an answer in the £hundreds-of-millions or £billions range. The implications of an incorrect decimal point in a key, but deeply buried, cell are massive.
It makes me come out in a cold sweat when I think too much about how they'll have evolved over the course of months as the conceptual model or the personnel involved change. And by "evolved", I mean sheets added, hardcoded numbers stuck in "just for now", etc. And, naturally, the final changes will have been made to an immovable deadline - probably at 0300 by some poor sod who's not slept for two days.
I've seen this in several industries and both public and private sector - if anyone is practising Excel discipline, I've yet to encounter it.
And, another thing: version control! Don't even get me started!