Conjecture

I have a feeling that the three sites most linked to - by way of footnotes and explanation - are Wikipedia, Amazon, and IMDb. Why is that the case?

Aside from being the standard sources in their various neighborhoods of information, these sites are exhaustive and dynamic. They are hubs, not dead ends.

Rather, Wikipedia is a hub. (Perhaps the hub at present.)

Amazon and IMDb are really just overlarge cul-de-sacs, aren't they?

You can get from Wikipedia to Amazon or (IMDb). *Can you go the other way around?

*All roads lead to Amazon. Evidence that desire and commerce are stronger than the search for knowledge and geek-status?