Information, and beyond
Now, we come to the bit that is ignored by many of the 'accessibility' gurus. With the preponderance of the 'document' concept and all the technology and technologists, the emotive aspects of 'design' are often overlooked. Whatever they say, a picture is not a document. A Flash movie is not a document. The Web is no longer all text! If the major part of a Web page is not text then all the rules fly out the window.
"Okay", I hear them say. "In addition to your Flash site, also provide a plain HTML version." Sometimes you can and sometimes you can't. Who is to say that your Flash site is not 'Art' and has no text equivalent? There is no law that says that a website can't be purely visual with little or no text at all.
Without going to that extreme, why not combine some of the emotive undertones of art and visual expression with the pure informational aspect of text. Graphic designers have been doing that for a very long time. If you draw a line between function and style, pure information will be at one end and art at the other. There are a lot of possibilities in between!
Most marketing communication involves more that just plain information. It's not what you say, it's the way that you say it! A message with a high style content is more appropriate for some sites than others. Where it is possible to make the information part accessible, the visual style aspect, which might be of equal or even more importance, could easily be lost. The visual requirements of selling a local plumbing service on the Web are quite a different story from selling the latest Mercedes Benz.