Russia’s Yandex search engine (Google’s competitor in Russia) uses two operating systems, one of which is FreeBSD.
Any surprise? No, FreeBSD stays rock solid under heavy workloads. Yandex is now looking for managers to work with one of the largest and most complex IT systems in Russia.
More about the job vacancy (via)
Yes yandex use Freebsd, and have mirror ftp6.ru.freebsd.org and cvsup7.ru.freebsd.org.
And research network driver http://people.yandex-team.ru/~wawa/ ;)