We sort of are. My company does anti-spam and email security for over half the fortune 500 with 3000+ employees. We use FOSS everywhere. We contribute absolutely nothing back afaict.

We are trying to recruit people who use these open source tools/languages and literally no one has ever heard of us. Forget college graduates -- I've been to an industry conference which I think we create, and even there, the majority of people have never heard of us, which is imho an accomplishment.