As has been discussed by a few different posters, there are certain professional groups that require membership in a larger organization (i.e. Medical Personnel) that enforces ethical practices.

I would argue that, in modern society, the only reason to have a written code of ethics is to enforce it. Every individual has a pretty good idea of right and wrong; they're going to make their own choices regardless of what's written. Having a well-defined code of ethics allows an oversight entity to point to it and say "this is why you're disbarred."

Until and unless there is some overarching DBA professional organization that everyone belongs to (and that has power to enforce ethical policy) there is no point in creating a DBA code of ethics.