Brent points out that there’s a non-trivial cost to supporting multiple kinds of weblogs in a blog front end tool like NetNewsWire or Manila Envelope. Weblogs may look alike on the surface (and to an RSS aggregator), but they’re all different software platforms underneath and accordingly have different information needs. This is fine as long you don’t have to expose the mess to the user.
This is one of the reasons, I think, why the MetaWeblog API came about. Abstracting the common elements of the data elements into a new API layer is smart. Unfortunately not all the platforms support it…