[Consultant32452]

In my experience the only thing that prevents that phenomenon is unrelenting stubbornness from the development staff. It takes a tremendous amount of thought and care with each change to make sure it doesn't happen. Also in my experience, there is no "fixing" it once things have gone down hill. It's theoretically possible, but I've never personally seen it happen. Whereas I have seen fairly large code bases remain coherent after years of significant changes. That dev team was like a bunch of nazis as far as code quality was concerned. It was the best team I've ever worked with.