Erlang is a "telecom language" because based on "asynchronous message passing interface". Of course this avoid shared memory and thus locks, but it leads to duplicate information maintained in several processes, a need to keep it synchronized and a lot of crossing cases. Moreover lots of external interfaces like database access are not easy to use in an asynchronous way. In term of efficiency, you do have lock as a process cannot deal with the following message until it has finished with the previous one. You lose time as well in process switching and because each process has first to find to which information the message it received applies to. »