Comment by pjmlp

Facebook is using Haskell to control spam.

https://code.facebook.com/posts/745068642270222/fighting-spa...

Galois uses it for their financial products,

https://galois.com/about/haskell/

A German company, CMED, uses for their medical services server

http://cpmed.de/jobs/haskell/

Other than that, not all companies are found of putting all their golden eggs on Github.