I do realise I'm basically describing Gopher here, and there's possibly a reason it didn't take off...
If only browsers provided better defaults. As it stands, very few people would consider the browser defaults acceptable.
> it's no surprise Wikipedia uses black text on a white background with blue hyperlinks
Yes, Wikipedia does use black text, a white background, and blue links. But they do not merely rely upon the default browser stylesheets. They use custom font-face, font-size, line-height, and margin properties even for the basic <p> tag. And that's saying nothing about all the other elements that often have borders, padding, backgrounds, and so on.
There's a lot to be said about the Svbtle/Medium-style design with a small column running down the center of the page.