Unless you have horrable retention issues highering someone who does not know the language your using is not that big of an issue. Taking a C# ASP.NET developer > Ruby on rails is faster than bringing a Java developer who knows nothing about the web into a large Spring/Struts project.

That might be true for a basic/early Rails app where it's ok to have script kiddie relationship with Ruby, but if you have a more complex app, I don't think the learning curve is quite as easy as you're making it sound.

My own experience with Rail is that I quickly wanted to see inside and control all of the implicit stuff that was going on, and I needed to invest a lot more time to learn Ruby to have the knowledge that would give the amount of control I wanted.

Hiring any programmer that can't adapt to an unfamiliar new language is a bad idea (TM).

I'm far from a guru, but I've been able to pick up quite a few different languages, frameworks and structures over my tenure. It's the ones that limit themselves to a single language (be it Java or not) for long periods of time that you need to worry about.

These are the programmers that will build a square wheel because that's what the spec told them to build. Employ them at your peril.

That's cool, but when I'm hiring a team and paying their salaries with my own money, I'm just not going to bank on transitioning anyone from X to Y. No time for it, no appetite for the risk. But if you raise VC, more power to you.