I fully agree with this post. And it would not surprise me if parallels could be found with the so called 'Broken Windows' (no pun intended ;) theory from criminology.

http://en.wikipedia.org/wiki/Broken_windows_theory

That is, similarly to how a messy, run down environment invites anti-social behaviour and crime, the less tidy a code-base is the more corner-cutting will be invited on more structural levels as well...