Given that you will have to figure out scaling issues eventually anyway, the speed of compiled languages should NOT be weighed heavier than programming ease in your decisionmaking. Programmer time is FAR more expensive than hardware these days.
Ruby is great at what it does. I don't see Node.js replacing it anytime soon. But Ruby won't be in enterprise anytime soon also.
" If another language can provide 10x more performance in 2x the code of Ruby, that's a tradeoff I'd seriously consider.
If I do ever have a hit on my hands, and it starts scaling quickly, there's a cost, management, and maintenance issue to bottlenecking myself with Ruby. "
I realize that there are many parts to a system and that other parts encounter scaling considerations before the programming language does - ie database.
However, it seems there are known, quick to implement solutions that can solve the data scaling problem in a cost effective manner. Reimplementing my application logic with another language seems to be a very cost-ineffective and time consuming task.
I'd rather head that concern off at the pass by picking that language with 10x the performance and 2x the amount of code.