Well, at risk of trying to read the mind of your parent poster, I suspect it seems odd because that person thinks that working at Facebook is unlikely to (for a junior employee) involve stimulating work, interact meaningfully with Facebook's scale, or build skills necessary for more senior-level work later in one's career. And be frustrating on an organizational level and involve working at a kind of douchey company.

And right now, I think there's at least a perception that the instability of smaller companies is compensated for by a very strong job market, that you can find very smart people in lots of places, and that most of the non-monetary benefits are unlikely to be really worthwhile at least for young healthy people. Leaving basically pay as the differentiating factor.

I don't whole-heartedly endorse the above analysis, but I think it has large elements of truth in it. If my hypothetical 22 year old niece told me she had job offers from Facebook and also from a small start-up, I suspect I'd advise her to take the Facebook job and quit 1-2 years later. But I'm not sure my advice would be correct.