Out of all the "killer apps" for the web... wikipedia is the one that implement the www most faithfully. Hypertext articles. Most apps got the web to do x. Wikipedia is what it was made to do.
Yeah. I was about to add that it pretty much has been Tim Berners-Lees vision coming to fruition, but the fact that Wikipedia is centralized has stopped me. But then isn't the Web itself technically 'centralized' on the Internet ? And isn't Wikipedia a great example of pseudonymous strangers (= social decentralization) collaborating with each other ?
Is it really that centralized? Citations and footnote links are a pretty important part of what wikipedia is. I mean, I very rarely click through to see source material, but when I do it's noticeable how much more powerful wikipedia is than a standard encyclopedia.