Simply put, Yog.0 is the Anarch card with the most impact of the Core Set. It was so strong that for a while (including at least a few store championship level tournaments) players were including only a bare minimum of code gates. There was even one deck that only had a single code gate at 3 copies, simply to force the runner to install Yog and then have it be useless memory for the rest of the game.
It’s ability to break for free, any number of subroutines, even though it is on a fixed strength, makes it one of the most dangerous Decoders in the game. For a long period, any Code Gate of 3 or less strength was simply dismissed as being too weak, because of the prevalence of Yog.0.
Even today, Yog.0 is still something that must be contended with, though as Code Gates grew in strength, its dominance of Decoders became less apparent. The arrival of the Yogasaurus (Yog.0 on a Dinosaurus) and in combination with Rielle "Kit" Peddler: Transhuman and a possible Paintbrush means Yog was still a threat - if not seen nearly as often in that manner. Yet no other Decoder, and no other Anarch card left players scrambling to deal with it in their corp deck designs, affecting the game as much as Yog has, and will, over the years.
(Written during the meta of The Valley, part of the SanSan Cycle. For more reviews like it, visit wyldside.blogspot.com)