Twitter's loss is your gain, another post!
"But as Twitter's popularity grew, the Ruby-built back end wasn't able to handle the torrent of messages that came its way--a situation that created the sudden popularity of the "Fail Whale," the error message that Twitter sends to users whenever the service crashes."
So, let's see what's happening right now on Twitter...
UH OH. FAIL.
RoR doesn't scale (I was going to go to RailsConf just to see what not to do, thankfully I came to my senses and cancelled my trip) so they switch to Scala? If you want scalability, you need more than a language, more than a framework. Now Twitter has a better language, but they've inherited all of the JVM's scaling limitations.
Scaling is more than a language, it's more than a framework, more than the VM. I fear the Twitter tech people are too easily won over by hype.
Scala is not bad, it's a cool language, but it is not the solution to Twitter's scaling issues. Of course, we'll probably find out the outage is due to a database or hard drive crash or something, but my point remains.