What previous project/technology is Wikipedia copying?

No one will read a Wiki, no matter how good it is, unless they're led to the information and can find it if they're looking for it.

While Google's "hegemony over web searching" (in the U.S.) is in some ways regrettable, it does provide a quick and easy way to find quality content (e.g. Wikipedia, though I take your point about some poor quality articles on that site).  So effectively content -- if it is deemed "good" by enough people -- can become media thanks to the exposure it gets via Google and other online "bottom-up promotional" mechanisms, e.g. basic linking, Digg, del.icio.us, etc.

But maybe I am not understanding what you mean by media.  Is DailyKos media or content?  Huffington Post?  Does something become "media" simply when it gets over a certain threshold of regular attention?  If so, why couldn't EuroTrib-cum-ETWiki also count as "media" if and when it gets the same kind of exposure?

A language is a dialect with an army and navy.