Also I thought it was interesting about the rise of F#. That is a language that looks really cool, but it's tied to the whole Windows/.NET environment. Of course there is still mono. Has any had any experience with F# in mono, and know if it is as performant as the windows stack?
A language could be at the top simply because it forces people to ask a lot of questions on StackOverflow.
I'd trust GitHub's language activity much more than something like Tiobe -- http://langpop.corger.nl/
Overall, Mono isn't as fast as the .NET CLR on Windows, but it has improved greatly over the past few years (since Xamarin took over development from Novell and hired a team of full-time developers); in fact, a couple of months ago I saw a post here on HN about an HFT firm who'd built their trading stack on Mono.
As for F#, it's usually quite speedy, whether you run it on Windows or Mono (OS X, Linux, FreeBSD, etc.)
EDIT: more searches:
I do not work in large enterprises. In the universe that I inhabit, Ruby is popular and C# is unknown. I have always been curious that my own career seems so far out of step with what organizations like TIOBE show.
If it turns out that langpop is the most accurate of the data surveys out there, then it deserves credit for correctly showing the rise of Ruby.