[prodigal_erik]

http://en.wikipedia.org/wiki/Communicating_sequential_proces... works well passing immutable object graphs back and forth. Passing by value (copying everything) has a cost, and serializing everything down to byte streams across a pipe is even more expensive, especially if you don't know which portions of the object graph will and won't be needed for a given call (an optimization which imposes tight coupling on details about the code you're calling). If I'm not calling untrusted code, and not planning to divide the work across many machines, I'd prefer to avoid needless process boundaries.