"Wikipedia says software erosion is "slow deterioration of software over time that will eventually lead to it becoming faulty [or] unusable" and, importantly, that "the software does not actually decay, but rather suffers from a lack of being updated with respect to the changing environment in which it resides."

Если еще не читали 2 статьи на близкую тему в блоге Ивана Сагалаева, рекомендую прочитать: Вместе или врозь, Вместе или врозь: новая идея