The ErlangVM has a scheduler and fly-weight processes on the order of
300 bytes each, so you can have hundreds of thousands of tasks in
flight on conventional hardware.

If I understand Clojure actors correctly, actors will not need a
dedicated stack, heap, or mailbox, so an actor could be as simple as a
reference (4 bytes on 32 bit machine), so you could theoretically have
tens of millions of actors in flight and process them with a
conventional thread pool?

Wow, can't wait to try it out.