Follow-up on this, I found the article again. As I thought, I came across it on Raymond Chen's MSN blog "The Old New Thing". But since the search on that blog doesn't work at all (??) I wanted to write him an email about it and while googling for THAT I found the original thread
"How Microsoft Lost the API War" on Joel on Software that links to
"When programs grovel into undocumented structures..." on Chen's blog. Another link goes to
"What about BOZOSLIVEHERE and TABTHETEXTOUTFORWIMPS?" there, which is also entertaining to read.
On behalf of games breaking upon Windows Updates, he writes about that in an older article named
"Why not just block the apps that rely on undocumented behavior?", which is referenced on the Wikipedia article about him, too.