Twitter said to be abandoning Rails
"But let’s be real for one minute. Twitter doesn’t suck because of Rails. Twitter sucks because they have ridiculous amounts of traffic (especially to their API and SMS gateways), a limited ability to cache (a non-realtime Twitter is a pretty useless Twitter), and (as far as I can tell), they’re not making any money, so they probably have limited resources to pour into more hardware." (via)
Well said, Jeff. Even if you do want to see them use Django.