With the latest version of my collaborative website platform, I'm actually starting to migrate business logic from data structures... if I did it full and proper, I'd just double all of the beans, so far as I understand things (I don't quite, really...) I'm not that hard core at the moment. That could be because I don't have as much of an understanding as other folks, yet. Or maybe it doesn't matter to that extreme. I don't know.
What I find truly sad is that after railing against it as a waste of time and code... I started doing it just because it seemed right in certain circumstances. Didn't strike me that what I was doing was "proper" until hours later. oy me.