"In cakes, more layers is good. In software, more layers is not good"... Except that the skill sets in the layers really are quite different, and the time is long gone when one God-like mind can comprehend the whole of a software system both in its large-scale aspects and in its details. So the DB person knows a bunch of stuff that the UI/UX person doesn't know and (hopefully) doesn't need to know, and vice versa. In fact, software developers come in at least two flavors: systems people and user people. I wouldn't want a user person mucking around with my DB schema, and I certainly wouldn't want a system person designing my app workflow. And it's probably worth protecting these specialists from one another. I'm not familiar (as a practitioner) with Ruby/Rails, but I do remember ColdFusion vividly, which was used (with one name for UI fields and DB fields, for example) to produce some monumentally un-maintainable, un-scaleable systems. Probably more layers is not good ad infinitum, but too few is courting trouble as well.