Interesting, but I wonder why they didn't take a look at Erlang - I mean this is pretty much what it was meant to do.
Kidding - I would be very interested in more on why Scala failed as well. Both Scala and Erlang are implementations of the Actor model and should theoretically be very well suited to this.
Offtopic: I'm not an expert on functional programming (just getting my feet wet; forgive me for being so naive), but after reading Scala By Example I have this nagging feeling that a functional implementation of an algorithm might actually run slower than an imperative implementation of the same algorithm. I mean, you're copying data all around the place, creating new instances of objects instead of modifying them in place, using a ton of recursion everywhere. Could anyone offer some perspective on this?
At the end of the day storing sockets in a hashmap is a pretty compact data structure. If you can minimize synchronization/locking, threads shared state is extremely efficient from a CPU and memory standpoint. Maybe not so efficient from a developers time/sanity standpoint though. :-)
Do note that this article is purely about an edge server though. Its job is essentially to hold sockets and communicate with internal queues. The message passing model is alive and well, albeit at a higher level.