Just a quick post, I get asked this question all the time. What is MOST? Well MOST is an acronym for Media Orientated Systems Transport.
Most is generally found on Audi, BMW and Mercedes Benz cars. It is also becoming more common now with other manufacturers too. The MOST system is also known as the Optic Ring or Fibre Optic loop. It carries the audio and sometimes visual signals around the car.
It's basically a lossless audio transmission network, that suffers very little interference, if any at all.
Well hope that helps a few people out there.