While I don't know the exact answer to Justin's particular case, I'll say it's not uncommon for someone to be already proficient in hacking at age 20. Zuckerber

While I don't know the exact answer to Justin's particular case, I'll say it's not uncommon for someone to be already proficient in hacking at age 20. Zuckerberg was a potential psych major when he launched Facebook, I believe at age 19 or 20. I would guess a lot of hackers on HN started young and already have several years of experience by the time they hit college. And by that point they might not even need to choose to study CS, instead rounding out themselves by studying other interests.