The incredibly interesting thing about this example is that it sounds like the design actually had to change in two ways: 1) the value had to be configurable an

The incredibly interesting thing about this example is that it sounds like the design actually had to change in two ways: 1) the value had to be configurable and 2) it had to be configurable on the fly. Anticipating and designing for (1) is simple enough - the costs that the article refers to are quite low - but to think ahead and design for (2) is a completely different task that might radically complect the code.