I read Almost Perfect, the story of WordPerfect Corporation, years ago, and have used the story of ‘the minor change that wasn’t worth testing before release’ many times.
“On Friday the 13th there were so many people trying to call us that our busy signals brought down the entire AT&T 800 system in the Mountain West. The phones in the Delta Airlines reservation center and the American Express customer service center, both in Salt Lake City, all went quiet. AT&T called around lunchtime to politely inquire how soon we could clear up our busy signals. Much to our embarrassment, we had no answer for them. We were in deep trouble.”