In end Chap 1, Cesarini / Thompson book, which is excellent, it talks about code SLOC difference vs. a C++ telecomm app: 85% of the C++ code is defensive coding, memory management, high-level communications, which are pretty much unnecessary in functionally comparable erlang code.
Take a look if you're in a bookstore or can borrow from somebody.
also read about research into hard realtime apps
http://lambda-the-ultimate.org/node/2954
http://www.scribd.com/doc/415282/05nicosi
