While I agree with the approach described, in practice things can be a little different. We decided to start using python in our agency a couple of years ago.

While I agree with the approach described, in practice things can be a little different. We decided to start using python in our agency a couple of years ago. We really love it but since that time we've really struggled to hire good people. Even in a big city like London we can't seem to find python devs that also have the other skills required for the agency world. When I interviewed for this job we bonded over a shared interest in erlang (4 years ago). You don't need to use it internally but if you have a candidate who is interested in something like erlang, they're (probably) deeply interested in programming. That's going probably a safer approach. Find people who do have an interest in the more obscure parts of software development (easy to gauge in a phone interview) whilst still practicing a more common language. My point is that there's a much bigger picture to language choice. I'd rather be trying to find perfect candidates from a flood of ruby cvs than struggling to find any candidates at all from insert lesser known language cvs.