I got an unexpected answer to my question from the last post. As I was driving this weekend, I was listening to a CD of archived Gillmor Gang episodes. During this one, at about 15:20, John Udell answers the question "why do you care about Atom's release?" by explaining that Atom is able to carry XML data as a kind of attachment, which RSS was not intended to do. His example was that you could carry information like reviews.
So people are thinking about how you would represent structured data like reviews. I asked the blogosphere, and the answer was already cued up in my player.