So this one interview question allows you to make the decision between hiring someone who has only worked in the profession for a month and hiring someone who wrote a whole bitcoin exchange. Faint praise.

The big issue is, what does this style of interviewing do for you with a real-world candidate selection challenge --- say, 3 developers, all similar on paper?

There is no reason the best candidate necessarily has the best story. The story of your "best accomplishment" has as much to do with random chance as it does with capability. This question demands that an interview somehow de-confound the luck element and the skill element.

And to what end? Even if you got a clean reading on this question, somehow equalized between the candidates, I ask again: do you really know a lot more about how the candidate will actually perform on the job? Because that is almost the only question that matters in candidate selection.

I'd say the question helps you separate out candidates who have run into this sort of BS question before and have a pat answer already prepared.

"Gee whiz, I'd say my biggest flaw is that I'm TOO passionate about technology!"

You misread my example, no beginner writes a ton of LOC, but yes. I don't think it's faint praise - some hiring managers would manage to find a reason to not hire the second guy, when the first one had been "employee of the month" already and that's good enough for them.

Seems to me a person with a single 1000-unit achievement would look better than a person with 1000 10-unit achievements if you ask about their single biggest achievement.

Maybe I coded an iphone app. Meanwhile you coded an iphone app, and fixed bugs in a huge legacy codebase, and did hiring and code reviews and mentored new employees, and contributed to open source projects, and introduced your company to source control and automated testing, and masterminded a trivial code change that made the company a million dollars a year, and you spend your free time running a programming club at a local orphanage.

If we're competing for a job and we're asked about our single biggest achievement, we'll both say iphone app. An employer who wants to accurately gauge who is the better employee should probably dig deeper.

Really? You wouldn't say, 'Saved the company a million dollars a year' or 'Introduced source control and automated testing into the company' ? To my mind those are much more impressive achievements than an iphone app (at least assuming it's a typical CRUD app.)

Depends on the interviewer, company and job.

Say I saved a million dollars a year by adjusting a configuration setting, no coding required. That might go over well with a business type, but if the interviewer is all about the programming, it doesn't demonstrate technical mastery. There will be no scope for talking about the technical challenges, the languages and databases I used, what I learned from the experience, or how much I enjoyed it and grew as a person and a professional.

Say I introduced source control and automated testing at a medium sized company. Again, the technical work is limited - you can install Jenkins with apt-get, the real challenges are political and educational, changing 'official' workflows and 'supported' software and convincing people to sink time into using the tools for long enough that they can see the benefits which are not immediately apparent. If I'm being interviewed by a young guy at a startup they might think they have no politics so my skills will be useless - or worse that I'll introduce politics. Or it just won't seem like much of an achievement, after all the six of us at this startup switched from bzr to git in an afternoon.

Needless to say, if the original job description says "wanted: someone to teach us source control and automated testing" that would be a different matter :)