Design-dead code

I found an interesting video by Ken Schwaber - Agile Quality: A Canary in a Coal Mine.

Here's the video (about 69 minutes long)

In it he mentions design-dead code (or quality-dead code), a very interesting notion that highlights something that I think I have always known.

The notion basically goes that the more you ignore refactoring and adapting your core (or legacy system) functionality to better suit your new features then the slower you go because you reduce the quality of the core. Whatever you don't spend on the improving the core this time will slow your velocity down by some relative amount next time (and every time afterwards). The worst thing is that it cumulates, as more features are added (and iterations continue) you will eventually get no new features because it's simply too hard to add them and your company will slowly, but fairly surely, die.