[untog]

But once you reach that level of scale you have (or should have!) the resources to redevelop services that are holding you back. Not choosing Rails because you intend some day to get to Twitter scale smells of premature optimisation. (Twitter themselves used Ruby!)

[fareesh]

Yep, which is generally why I can't see a good argument for not using it. I was hoping to see some here but it seems to be a consensus view.