This is a rather techie in-joke, but actually very funny: it is from xkcd, which calls itself "A webcomic of romance, sarcasm, math, and language."
In the Wikipedia, more and more, exact citations are being demanded, so that the texts have more of a scientific basis. Sometimes the fight goes too far, with editors insisting on citations for things like water boiling at 100 degrees Celsius, it seems. But overall this is the way we need to go: move from a copy&paste culture to a citation culture.
Thanks to a blog reader from Germany for sending me this link!