I meant literally, but by professional I meant "A-tier." I know of zero billion dollar software companies that use Haskell as their primary development language.
I know nothing about Facebook using Haskell. Last I checked they use a PHP-derived language called Hack.
I'm not sure what else they use it for, but they hired Simon Marlow, one of the main guys behind GHC a years ago. It's still not their primary language, but restricting the interpretation of "professional" and "uses" to what you had in mind is not the most interpretation of your comment to me.
I know nothing about Facebook using Haskell. Last I checked they use a PHP-derived language called Hack.