I do think that a blogger or board poster who follows these principles is more ethical than one who does not. That's obviously a broad-brush statement, as some of the principles are more important than others, and not all violations are alike. But in general, it's a pretty good statement of how the job ought to be done.
It's true that someone could claim to be following the code while in fact violating it. There is no sure-fire way to prevent dishonesty. But once someone has made an affirmative statement that they're doing something, they're a lot less likely to violate it than if they had never addressed the matter. For those that claim dishonestly to be following it, there is always peer pressure and media attention—at least in the more flagrant cases.
Oakapple - I don't misunderstand the intent that our "Fat Guy" has - I think it's an honorable proposal for what goes on within eGullet itself, I distrust that it could ever possibly be implemented fairly and honestly on the basis he proposes outside of these "walls". First, your first statement - while it's true, that someone who follows a code of ethics, be it this one, or the one posed over on new Food Ethics Blog site (which came out a week ago now), or someone else's, has those ethics (again, assuming they're not just paying lip service, but actually doing so), it's 1) that set of ethics, not the only set possible (the proposed one here, for example, is different in several ways from the one proposed on the site I mentioned), and 2) how does that make them more ethical than someone who has a higher ethical standard but never happened to hear of eGullet, or one of the others, or chooses to simply not sign their name to a statement? My point isn't whether or not people should be ethical and subscribe to a code, but it should be their own code, and one which they've stated for their own readers, at least outside of eGullet. Here, within these forums, I have no problem with the idea of a code that people are asked to follow - though we still get back to the second part - which is, just because someone says it doesn't mean they follow it.
Outside of a moderated forum like this, there is no peer pressure or media attention on the average blog/amateur writer - so no, I don't think there's anything out there that would stop someone from claiming they follow some code of ethics, posting a badge, and simply not abiding by it. Regulating the blogging world (or other types of privately owned/written sites) by imposing rules on what people are allowed to write about and how they write it is what I find chilling - isn't that what we all had a big blow up about a couple of years ago when there were rumors going around that the FAA or someone like that was going to start being a watchdog to the internet and what people could post? Who says a private, non-proft, arbitrary organization will do any better at the job? And when it comes down to it, I (as many bloggers do) pay for my own site - why should I have to be penalized because I choose not to display a badge from an organization that has set itself up to be the arbiter of ethics? My own readers know what they can expect from me, I've stated it myself, and the lack of whatever lovely little piece of graphic work someone here comes up with shouldn't become something that new readers or the media (if they care) or anyone else can point to and say "he's not following the code, he's not a real food blogger" - and they will.