Actors are a model, I have no clue why you're saying that there is a particular memory cost to them on real hardware. To me, you can implement actors using fibers and a postbox.
I've no idea what the majority of programmers know or do not know about, but async logging isn't unknown and is supported by libraries like Log4j.
I remember Joe Armstrong saying something like 2kB in his talks, for an Erlang process. That's 1/128 of 256kB.
Yeah that was my also my thought.
I always understood that if you give a thread to each actor you get the "active object" design pattern.