DYK, or proudly displaying incorrect information on the Main Page with alarming regularity
"Did You Know", or WP:DYK for short, is the spot on the main page below the Featured Article, where new or newly improved articles can be shown. At the moment, 16 articles are highlighted every day on the Main Page with a one-sentence hook each, which gives some 500 articles per month a short but highly visible stay in the spotlights. During the twelve hours a hook is normally on the Main Page, the MP is viewed some 5 million times, and the articles bolded in the hooks typically get a few thousand views each: the number of readers per hook will obviously be somewhere between those two figures.
DYK hooks are normally checked by at least four people before they reach the Main Page: the article nominator (often the person who created or expanded the article), the reviewer and promoter (two editors who check the article and hook on the individual DYK nomination page, transcluded on Template talk:Did you know), and the person (an administrator) who creates the DYK sections for the main page (Template:Did you know/Queue). That's four people for every hook, and at the moment 16 hooks per day. Shouldn't be too hard?
I have written a few DYKs, so I know that part of the equation. It isn't always easy to expand an article sufficiently to make it long enough for a DYK, and many articles have no interesting hooks to highlight them with. My first DYKs, back in 2007, were for Happy Hooligan and Winnie Winkle (which later became a GA as well), and more than twenty followed over the next years, on topics like Cromwell Dixon or Achilles on Skyros. I started to look more at other DYKs at the same time, and noticed some errors and problems. My first comments were in Wikipedia talk:Did you know/Archive 87#Template:Did you know nominations/Gibraltar Rock, Porongurups. Earlier archives contain many complaints from other editors about accuracy and errors. Over the next two years, I removed many hooks from the preparation area and from the main page for having (sometimes blatant) errors.
Many suggestions to improve DYK were proposed: not showing nearly every proposed article but only the best or most interesting ones, limiting the number of DYKs per person (to get more variety instead of dozens of hooks on very similar topics), adding more reviewers, banning people with many problematic (incorrect) DYKs from nominating more pages, even abolishing DYK altogether. Some things, like the suggestion that one shouldn't only look for a source confirming the hook, but also for sources contradicting the hook, were seen as a good idea, but (as the below examples will show) have not been implemented.