various Common Lisp network servers are threaded and each thread takes up 2-4MB of heap. This limits the amount of threads that can be spawned.

With Erlang I can just launch a process to handle my incoming request, one process per request, without worries.

For comparison, Gambit Scheme takes about 1k per thread. Thread creation appears to stay under 3 microseconds as long as the heap remains abundant. These numbers are essentially the same as Erlang's. http://www.erlang.org/ml-archive/erlang-questions/200212/msg00058.html Obviously room for improvement in CL if any of the providers take an interest in highly concurrent systems. -Patrick