@Andy

Perhaps Wikipedia's underlying zettelkasten nature is hiding in the more narrative nature of the ultimate pages, but it's definitely there. The "standard" web user interface view of Wikipedia pages makes it less obvious that the added pieces are atomic in nature, and that Wikipedia in fact is a group zettelkasten being built in the public/commons. However, if you've customized your own specific view of Wikipedia; are using an Atom Subscription (and yes, it's actually called this!); watching recent changes; or are using the history functionality (example: https://en.wikipedia.org/w/index.php?title=Zettelkasten&action=history), then you're getting closer to the sorts of views of atomic additions I was speaking of. Some of this is also the reason that there is a checkbox for "minor edits" to take account of typos and minutiae which are sub-atomic and filters out or cleans up the stream of the updates one could receive.

Viewed from this perspective, Wikipedia is a distributed zettelkasten of the highest order. Intellectually all this traces back to the original zettelkasten of Konrad Gessner, who uncoincidentally is one of the most famous and prolific encyclopedists in history.

One could easily take small notes made in their own zettelkasten and add them on a 1-1 corresponding basis (including the note, the references, and even a unique identifier chosen and applied by Wikipedia; here's an example with the identifier 1118181304 as a demonstration) to a variety of Wikipedia articles. For certain topics I'm interested in watching, this can be a great boon to my own zettelkasten as I can reverse this process and subscribe to/watch additions at the smallest level and not only excerpt them directly into my zettelkasten, but I can usually locate the original source and excerpt directly from it as a means of verification/fact checking. As a result this zettelkasten being built in the commons on a daily basis can be imminently more useful to me. (Sadly, I don't think that many others are using it the same way or if they are, they're not doing so at the rate/speed/facility that I am.)

A similar example can be seen in the topically arranged group zettelkasten created for The Great Books of the Western World which was lightly edited into the book form of The Syntopicon (volumes 2 and 3 of the 54 book series). One could certainly try to argue that The Syntopicon isn't a zettelkasten because it is in edited book form, but in fact, it's just an easier published and more portable form for me to have a copy of Adler and Company's physical zettelkasten as the end product is a 1-1 version of their card index with some introductory material added for readability and direction. The sad part here is that Adler's zettelkasten has ceased updating in 1952 while Wikipedia continues apace.

For the "fans", one might say Wikipedia is even more closely related to Luhmann's variation of a zettelkasten as the user adding a particular idea doesn't need to add explicit links to other external ideas (though they certainly could), but by placing it on a particular page in a particular paragraph, they're juxtaposing it to a specific location that closely relates it to nearby ideas which already exist in that particular page (train of though/folgezettel).

Certainly Wikipedia has a hypertextual nature as well as a text and document editing capabilities and dozens of other interesting and useful affordances, but at it's core, it's true soul is that of a (digital) zettelkasten.

Reply to @andy at https://forum.zettelkasten.de/discussion/comment/20462/#Comment_20462