Interesting. I've worked with Akka heavily over the last 3 years and that was built borrowing many of Erlang's designs. I'm sort of suprised to see that the language was not built with the intent of implementing the actor model. Fault tolerance through supervision was introduced into the actor model here but the way that state can exist and is isolated for high concurrency systems makes the actor model very easy to build into and reason about in concurrent scenarios.

Akka's addition to the actor model - location transparency - takes the actor model a little further and coupled with Scala makes a really nice language and concurrency pairing. Akka has the actor model as a library added where Erlang has all of the qualities built into the language. I'd like to learn erlang still but the contribution of the Erlang/OTP team in building fault tolerance into the Actor model has been an incredibly important contribution. As highly concurrent applications are becoming the norm with multicore CPUs being everywhere, I can't see the actor model going away any time soon.