Oh good. This is where I get to chime in. Twitter wouldn’t have existed with out Rails. It was a side project inside of a failing startup. It took Jack and Florian like two weeks to have a solid version up that we could all use and love. That’s two weeks of designing and then having Rails make it super easy to prototype. I was in the management meetings and my read was that if they’d wasted any time fighting with technology or gold plating infrastructure then we would have moved on.
So I do see Twitter as a huge Rails success story. To use the Rails term, Rails was the scaffolding. Replacing any part of Rails later isn’t a failure of Rails.