Structured blogging–what's in it for users?
Well, trying to make ordinary users add more structure to a blog entry is a non-starter. The way to go is to find people who are already entering structured data, and allow them to do it to their blogs.
The clue here is spreadsheets. Dan Bricklin is on the right track with WikiCalc, although the UI isn't right. But what about a plug-in that lets you post to a blog directly from Excel?