A Yognaut, or Yognaught, is anyone who is a fan of the Yogscast.
Every Yognau(gh)t's name is Dave!, and is instructed to do the special Yognau(gh)t salute if they ever meet another Yognau(gh)t in public. The salute is done by claiming that you are both Dave! Yognau(gh)t, and that you have the balls (see Dave! Yognaut).
In "YoGPod 26: Your Grandad Was A Bee?", The Yogscast have instructed people to call themselves Yognauts if they prefer Lewis, and Yognaughts if they prefer Simon. The reason being that Lewis thought of Yognauts as being like astronauts, while Simon first used Yognaught because, as he said, it's "Naught, as in nothing".
The reason both are being used is because Simon likes the fact that he is getting someone to spell a word "wrong", even though it is a word they made up.
According to Google, about 75% of Yognau(gh)ts are actually Yognauts.
Further variations of Yog sub culture from an Eco-Socio-Biological-Fundamentalist PerspectiveEdit
As naturally happens on occasion, certain members of the Yognau(gh)t collective engage in commentary that, in polite company, would be considered to be at least a little bit cheeky, and amongst the erudite and refined upper crust of the Yognau(gh)t elite, (pretty much just Dave), would be considered down right scandalous. These people fall into the generally social self identified sub group known as the Yognaughtys.
Then of course there are people who deny the entire phenomenon of Yogsnau(gh)tery, and those people are simply referred to as the Yognots.
Zombienaughts, mentioned during the Yogscast play through of Hypixel's Wither's Challenge, are a cult of undead Yognau(gh)ts that have become zombiefied, and oppose the Yognau(gh)ts.