In Erlang the concurrency model is (always) a distributed one and in Clojure it is not. I have some reservations about unifying the distributed and non-distributed models [..], and have decided not to do so in Clojure, but I think Erlang, in doing so, does the right thing in forcing programmers to work as if the processes are distributed even when they are not, in order to allow the possibility of transparent distribution later, e.g. in the failure modes, the messaging system etc. However, issues related to latency, bandwidth, timeouts, chattiness, and costs of certain data structures etc remain.
