What have you developed in your spare time?

There is an implicit assumption here: that your day-to-day work does not consume all of your programming cycles. As a graduate student this was true, and now as a researcher in industry it is still true. The most interesting thing I'm working on now, the thing that is most likely to make the biggest impact is my work.

Everyone I know who was able to turn their passion into a profession have found themselves with diminished drive to work on their pet projects in that field. If someone is satisfied with their work, it gives them time for other hobbies. It is an unbelievable good thing if people can find time for multiple passions in their life.

Aside from the fact I think this line of reasoning is useless there is another -- more important -- issue. I don't care what people do in their off time. That's theirs, not mine. It is the same reason that I don't drug test.

Personally I believe often it is the only time you can truly learn. Often you are being paid to do a job, and in my experience (agency work) that job has been the same thing day in, day out, rarely properly learning new cool stuff to play with.

I wrote an article on this recently.

What’s the most important thing to know as a developer? http://sydl.me/1thingtoknow

I want to keep learning new stuff... the only way to learn is by playing with it. So I create stupid little sites quite often http://instac.at http://isitherapture.com http://obamasmessagetoamerica.com

The list goes on...

It's easy to point out that this question will exclude some false negatives, good people that don't have side projects. I rarely hear anyone worried that it will produce false positives, crappy people that have a github profile bursting with interesting work.

But here's the thing: If you think that this is a bad question to ask in an interview, I have a challenge for you: Describe a repeatable, objective process for interviewing developers. No hand-waving "I talk to them and decide if they're smart." Be specific: What questions do you ask? What constitutes a HIRE, what constitutes a NO HIRE?

If you actually try to make a repeatable, objective process, you realize that there is no fair interview question. It's impossible to come up with a set of criteria that can't either be (a) gamed by false positives, or (b) overlooks good people as false negatives.

For example, "Successful experience in a similar position" is an excellent criterium. But we all know it overlooks false negatives, people who have done good work in dissimilar positions but will adapt and thrive in this one.

In the end, we must either 'fess up and admit that we make subjective decisions, or set our jaw and accept that some false negatives are a necessary and acceptable cost of trying to standardize our hiring process.

(That doesn't mean we can't minimize the number of false negatives. One way to do that is to ask many questions and to incorporate all of the answers into your decision. If you're very conservative, you take any negative result as a NO HIRE, which leads to having more false negatives but a vanishingly small probability of a false positive. But you can go the other way and allow for some of the answers to be negative, which will create a vanishingly small possibility of a false negative overall but allow some acceptably small probability of a false positive.)

I enjoy my side projects, but to be honest, I work with people who are better engineers than me who never do engineering projects in their free time. I think it's an interesting question, but not as valuable as the author suggests.