Look, a PhD is for one thing, and one thing only: Teaching you to be a researcher. You're basically an apprentice researcher, learning from your advisor and others in the field the current state of affairs, the language they use, the questions that remain unanswered, and the methods you can use to answer new questions.

A PhD is not proof that you're smart, or that you cannot get a job, or of anything else (positive or negative). It just proves that you've demonstrated an ability to do original research, and to survive a system that is often unfair in numerous ways.

It also implicitly assumes that you're young -- and better yet, single and without kids. In that sense, it's sort of like a startup, in that it consumes as much of your time and energy as you're willing to give it.

I went into my PhD program knowing that I wasn't going to be a researcher. I went in planning to learn new things, to meet new people, and to maybe try some new directions in my career. In the end, it took a very long time (11 years), cost my family and me a lot of time and money, and didn't directly affect my career. And yes, there were lots of tears along the way, as well as many angry words.

I'm very happy that I finished it, rather than give up in the middle (which I considered on many occasions). I have a huge sense of accomplishment. I learned a ton, that's for sure. And we had an adventure living in Chicago, where I met many new friends.

But I tell people, very seriously, that if they're thinking of doing a PhD, they should think very hard before starting it. It's a huge commitment of time and money, and especially in the computer industry, there are ways to do research nowadays that don't require the effective vows of poverty and servitude associated with graduate school.