-The great Japanese Mugen collapse: I don't believe a proper name was ever established for this, but the shutdown of Geocities, Yahoo Japan and InfoSeek (and probably some other hosts I've forgotten) resulted in many, many, many, MANY Japanese Mugen creators losing their hosting.  I seriously cannot emphasize enough how scary this was at the time, because the Japanese community hadn't really adopted file sharing sites for their content the way we did in the West.  Some of them did eventually start using things like OneDrive and other uploading services (and still do to this day) but many others would be lost if not for the Wayback Machine and people having already downloaded their content.  We narrowly avoided a digital Library of Alexandria burning.