From the post: "recorded exactly one bug against their system" I guess it depends on what the definition of "record a bug" is. Sometimes someone can writeup a "user story" to change the desired behavior. Thus, no bug.
I'm not knocking the quality aspect of XP, but there are no industry standard definitions of bugs. And recategorizing things to make them not bugs is common.
For an analogy with retailers and ordering metrics, there are actual *standards* that define what a "perfect order" is. You meet all the requirements for a perfect order, and you can count it. Otherwise, you can't. Period.
Darrell: sure, I was just using this "1 per year" as an extreme example. Obviously the world isn't *that* wonderful, but Fowler lists some more realistic stuff in there too. I still love those numbers.