In the startup world, we (rightly) focus on growth, but it's worth remembering that there are giant companies out there using really, really boring technology. In some segments IBM mainframes, DB2, and COBOL are still the technologies of choice.
These entities are now having huge problems trying to get off 1980s or 1990s non-boring non-standard technologies that are no longer supported.
There are places that have bought the company that was going insolvent that built their non-standard database or framework....
"Nobody ever got fired for buying IBM" had good reason behind it.
How many of those were really engineers, rather than managers, marketing people, consultants, support?
"9,199 employees as of December 31, 2014" -- that's probably close enough to his metric to call it a large-scale engineering organization.
Of course, there's the real question of why Facebook needs to be a 10k+ engineer organization. For a minute it looked like they'd grow past their MySpace 2.0 roots. That becomes less convincing every day.
Maybe 1/5th of that are software engineers of any sort. Sales, marketing, management, admin staff, QA, sysadmins, etc tend to fill up organizations.