Or the lack of the most basic elements of a media library: folder watching. No, I don't want one folder, I want to watch any folder. Seriously, how fucking complicated is that to implement?
Given the default behavior of organizing all of your media within the iTunes directory, it makes perfect sense and would be a great feature. I'm sure there are other people more qualified to comment, but my first impression of the problem is that without some clever implementation there would be some major speed issues with large libraries.
I was thinking that you meant live monitoring, i.e. your library would be a reflection of your directory structure with additional metadata stored in unit sections so that it scales better.
I mean, a solution is out there: very good. Nevertheless, it doesn't justify or excuse iTunes for not having this feature.