Sure, not terribly interesting, but I got sick of people adding random "facts" without a source so I decided to use a reverse footnoting system to highlight it. Normally you add a citation footnote to clearly show where you got your fact or idea, mine was the opposite - it showed clearly that there was no citation so use the information at your own peril!

I also did it to force the editors to get sources and not just make stuff up. There was also often an issue where the fact was good, but was extraordinary and needed a source to back it up. The tag allowed the good info to stay until a source could be found. Unfortunately, sometimes bad info stays too long but it has the tag so at the very least you know that something is potentially fishy.

It was basically more wildly successful than I ever imagined. I really had no idea I was creating an important bit of Internet popular culture - I was just trying to make Wikipedia more reliable!