[boredtofears]

The problem I often see is in the evaluation of the naive cost of fixing it versus the actual probability your target of opportunity will become a legitimate design consideration. The naive cost almost always is large but the probability your target of opportunity will be necessary is often small or miniscule. It's easy to try to cover all your bases and write something in an unnecessarily flexible way when a concrete implementation would have solved the immediate requirements succinctly and very likely may not to be touched again for years (if ever again).