Can iTunes Genius (or song metadata) be improved so songs without a match can use the feature?
The way I understand it, Genius not only uses your mp3's metatags to organize Genius information, but also gets a lot of information from what people put in their playlists. This makes sense, as the point of Genius is to automatically put together a list of song that go together, without having to do it manually.

I read an article about this once, where a guy had Genius create a playlist for him, and he couldn't figure out for the life of him what the songs had in common. They were from all different years, genres, etc., even including spoken word. Finally, he realized that the tracks all had one thing in common -- they were Canadian. Of course, this isn't the most intelligent behaviour as tracks that are Canadian are not necessarily those you would like to listen to in succession. But of course, it would not be uncommon for people to create a "Canadian" playlist for other reasons than listening to it as a collection, and that's why Genius thought they might go together. The Genius feature slowly loses its charm as the track progresses from Celine Dion to a CBC Radio archive to (heaven forbid) Justin Bieber.