My guess is that most people using Haskell (and OCaml and Standard ML) are using it for internal tool such as program verification/analysis/transformation. It's

My guess is that most people using Haskell (and OCaml and Standard ML) are using it for internal tool such as program verification/analysis/transformation. It's not that Haskell/OCaml/Standard ML should not be used for backend services (i.e. APIs in a hot spot [at faceboook's scale anyway]). It's just that (in my experience) they're most commonly used for out-of-band analysis or developer lifecycle systems.