[daleharvey]

Not necessarily because it is functional, but Erlang makes this vastly easier.

I find the "oh you changed tiny piece of logic, you should totally have to refactor every line of code that follows it" very strange. It obviously sucks, there are far better ways to handle it and they are slowly making it into the language.

[fzzzy]

Erlang makes it easier because it enforces no shared state between actors, and each actor has it's own independent thread of control.