Eh, you can migrate bad data to a better model, too - and you can write code in such a way that you paint yourself into a corner that makes rewrites, especially incremental rewrites, very difficult.
I just mostly think that all these issues are just people being bad at writing software, and that if you're bad enough at it, you can crater your business. If it's only a little bad, the business can limp along until you can rewrite it.
