Here's an interesting question (after reading this).
Why does anyone want to write "large" programs? Everyone knows large programs are difficult to build and maintain. Want we want is *small* programs that happen to be powerful (do a lot) and scale over large numbers of users. Is there any reason to think that "large" program correlates with either of these things?
Supplimentary question. Are 10 programs of 1000 lines each, which have to nevertheless interact (via pipes or XML-RPC calls etc.) actually any easier than one 10000 line program?
Update : Folknology has been making a pretty decent case for Erlang as a language optimized for writing software as a swarm of small programs.