Facebook runs a low-support model. At the same time, they offer a lot of perks to their developers. I haven't been to their HQ but from my experience with other companies I would guess that a significant part of the people working there (20-30%+) are working in maintenance, security, hospitality, cleaning, restaurants, etc.
Keeping large offices running smoothly and in nice conditions takes an enormous amount of manual work, a lot of which other employees never see (much of cleaning/maintenance is done over weekends and at night).