> Someone edits a factoid into a Wikipedia entry or posts it on a forum somewhere. [...] Then maybe the mainstream media cites it.
That kind of thing happened to the former German minister of defence Karl-Theodor zu Guttenberg, whose full name is
Karl-Theodor Maria Nikolaus Johann Jacob Philipp Franz Joseph Sylvester Buhl-Freiherr von und zu Guttenberg[0]
and not
Karl-Theodor Maria Nikolaus Johann Jacob Philipp Wilhelm Franz Joseph Sylvester Buhl-Freiherr von und zu Guttenberg
which the Wikipedia article claimed and the news magazine Der Spiegel cited in an article. This article then in turn became the source for the slipped-in surname Wilhelm on his Wikipedia entry.
While his real full name already sounds totally made up Der Spiegel actually published a correction regarding his name.[1]
[0] https://en.wikipedia.org/wiki/Karl-Theodor_zu_Guttenberg
[1] https://www.spiegel.de/politik/deutschland/in-eigener-sache-...