1. As the need to inform an audience increases, the greater should be the degree of finish.
2. As an audience's power to approve increases, the lower should be the degree of finish.
3. The larger the audience, the greater should be the degree of finish.
Interestingly, Jakob Nielsen mentions a similar effect in his Top Ten Guidelines for Homepage Usability Alertbox article. His point is:
Don't Over-Format Critical Content, Such as Navigation Areas
You might think that important homepage items require elaborate illustrations, boxes, and colors. However, users often dismiss graphics as ads, and focus on the parts of the homepage that look more likely to be useful.
In this case the web site audience clearly has the ability to approve your content, and either hang around your web site, or go elsewhere. By Henry's 3 principles they should not be given too finished a product as they will need to feel they have not been bamboozled into making the wrong decision.
Of course, this applies to marketing in interestng ways too. At the beginning of the sales cycle, the customer is looking more for information about products than for specific information about why they should decide to buy your product.
If that's right, then providing polished content works well when people are just looking to be informed, but the same presentation method will work less well when they want to make their decision. I wonder if there are any actual examples that prove this out?
