I don't think that quote is so un-serious, Zuckerburg is literally and rather specifically offering his friend private information of the users of Facebook, and

I don't think that quote is so un-serious, Zuckerburg is literally and rather specifically offering his friend private information of the users of Facebook, and ending with calling them "dumb fucks". To the extent that I am learned about Zuckerburg in his earlier days of Facebook by having read various biographical accounts, I can pretty confidently say that the seriousness of his offer and the seriousness in his calling Facebook users "dumb fucks" goes well with the rest of his persona and doings. But anyway, this is getting pretty off-topic so I'm stopping here.