Does it exist? I'm not sure to be honest. How does one go about determining the existence of something unwritten. Is there a secret handshake involved or maybe a secret decoder ring? Could be I'm making a mountain out of a molehill too. It could even be that the unwritten rules--whatever they are--are in fact written down somewhere but if they are it isn't in some obvious place like the MS website or even the EPBF website--or even the old existing rulebook. Copies of the rules and updated rules exist in both places of course--just none of the so far discovered unwritten rules. Now see if I'd known about this before it would have spared a lot of confusion and misunderstandings. Frankly I'm a little disappointed in Ulrich for not explaining up front that there were enumerated rules and then there were those other rules--but that's all water under the bridge. VFTD's purpose today is to bring as many of the unwritten rules together as possible and create a written record that can be referred to until the MS's new rulebook is released (or written) (or whatever.) Did you know UFO sightings are more common than new Millennium rulebook sightings?
Anyway, the first unwritten rule supercedes the current written rules regarding leaving/abandoning equipment on the field during play. You may, according to unwritten rule, leave anything other than enumerated safety related gear, goggles & barrel sock. In contrast the written rule eliminates players who leave any gear other than pods and squeegees behind. [This came up on the recent webcast during the finals when a player left the front piece of his barrel behind.] So you see how confusing it might be for players outta the unwritten loop.
And there's this one from the first event of 2013. No cameras mounted on markers will be allowed (anymore.) No explanation for why. Only that it is now in the (unwritten) rules.
There's two and I'm thinking there must be a few more. So if you are a Mills regular and know an unwritten rule or two please send it to Baca's mailbag so I can add it to the list.