In Web Organization is not Like Book Organization, I said that the TOC does not work at a large scale. It is worth talking a little more about why it doesn’t work, because it has important consequences for many of the navigational schemes that people propose for the Web and other large information systems.
The reason a TOC does not work at a large scale is that a small scale TOC acts as a list that the reader can simply browse, but a large scale one becomes a classification scheme that users have to navigate. If you can’t take the TOC in at a glance, or at least read it through comfortably, then you have to trace down particular paths in the hierarchy of the TOC, and that means you have to figure out the classification scheme behind the TOC. And that does not work.