Wikipedia Vandalism Fad
Wikipedia is a web-based free content (open source) encyclopedia that allows people to edit it. One of the major problems with the encyclopedia is how one can easily come in and add crap to it; at wikipedia, it's called "vandalism". YTMNDers have caught on to this for a while and have vandalized the site, submitting screenshots of their edits to YTMND. This has been called the Wikipedia Vandalism Fad.
Safety Not Guaranteed
One of the most vandalized articles are the ones related to Safety Not Guaranteed. The frequency of edits to articles like Safety and Time travel were such a problem, that they were protected during the prime of Safety Not Guaranteed. The fad has died due to the everybody knowing about Wikipedia's editing system—thus losing its novelty—as well as Wikipedia's ability to reverse vandalism quickly.
Happycat vs. Rude Kitty
On July 27, 2006 LostPenguin posted a YTMND of a side-by-side comparison of the British Shorthair Wikipedia article of one with the original image of the shorthair and the other with happycat, with the title "Wikipedia Afraid?". Xioyux copy reverted Shortly after its posting the Wikipedia article was semi-protected. Some supporters of the YTMND believe that Wikipedia is either against or afraid of NEDM.
At least one site has been vandalized so many times by YTMND users that the Wikipedia administrators have banned all but users with special permission from making changes. One such article is eBaum's World, especially after numerous people altered the "controversies" section to be a bit more biased (and others just vandalized the article in its entirely).
Safety on Wikipedia Example of YTMND-related vandalism