Traffic in public mailing lists and forums is certainly correlated to language adoption, but the correlation coefficient probably depends a lot on the character of the language community and the particular forum. So, you can't really compare popularity of languages by their message rate.

The following issues probably play an important role in explaining the relatively low "message rate" for F#:

- Although the F# compiler and standard library are open source software, they are not developed in the open. So, there's no public discussion of development-related issues and no developer community open and inviting to new members.

- There is no official central discussion forum. This forum was supposed to be the central hub for all F# related discussion, but over the last year participation has suffered due to technical difficulties (no email notifications, browser incompatibilities, ...).

Some possible explanations vis-a-vis Haskell:

- I'd wager there are many more F#/.Net related sites than Haskell-reated ones, so info is spread out a lot more. (The same would apply to Scala.)

- F#/OCaml isn't as mysterous as Haskell to most - it's not lazy by default, and although functional constructs are supported in F#, they are not required to get the job done.

- The entire ecosystem (dev. tools, libraries, etc.) is very well known, because it's just Visual Studio and .Net - so usually there's no question (at least from .Net developers) about what to call to get something done.