Actually,I just found that Scala's event-based actors are threadless. Scala uses a pool of threads to serve all actor requests. If I recall correctly, Erlang does something similar.
In event based actors, messages are processed with the "react" keyword instead of "receive", the
Actors tutorial explains how to use it
Also I found a detailed explanation of what happens behind the curtains in
Event-Based Programming without Inversion of Control Seems Scala's actors are almost like Erlang ones
[ August 11, 2008: Message edited by: Gabriel Claramunt ]