What makes Zuckerberg a hacker?

he made a website used by 800 million people?

You might not necessarily agree with the extent the word "hacker" is applied to nowadays, but considering you are in a site called "hacker news" you probably should

So what if he isn't? He still gets the props for writing so clearly about his preference for that approach to product development.

I suspect it's also a shout out to future potential employees that he doesn't intend FB to change focus or style as a consequence of going public.