Not really "new" news but I stumbled across this while trying to figure out why Twitter seems to be down every day these days.

http://www.techcrunch.com/2008/05/01/twitter-said-to-be-abandoning-ruby-on-rails/

“We’re hearing this from multiple sources: After nearly two years of high profile scaling problems, Twitterclip_image001 is planning to abandon Ruby on Rails as their web framework and start from scratch with PHP or Java (another solution is to stick with the Ruby language and move away from the Rails framework).”

Its hard to know in a scenario like this if it's the architecture, the framework, runtime issues, etc.

Anyone know the specifics behind Twitters performance issues ?