[alttab]

This is exactly what we do where I work - a lot of our programmers don't know Ruby when they walk in the door but that shouldn't matter if you choose the right people. I'm scared of choosing language or framework 'specialists' because they have a limited view on what programming is, and a cemented view on what it should be. The only exceptions I can see are when the specialization is language specific to the problem domain, IE C for high performance server or system code.

Programmers who advertise themselves as "Ruby programmers" or "Python hackers" or what-have-you come off as inexperienced and one dimensional. The best hackers have used the right tool for the task at and, and the best hackers have solved a wide variety of problems to require different tools.