ColonelHardisson said:
My point was that it seems nonsensical, based on what we know of real world technology. There is no reason to believe that anyone in the real world will go insane due to having cybernetic implants
Can you give me a reference that states that excessive amounts of cyberware drives you insane in Shadowrun? Or are you mixing SR up with Cyberpunk, where I know for a fact that it drives you insane?
In Shadowrun, if you go below zero essence, you die. Essence is what binds the soul to the body. When you go below zero essence, there's simply not enough left of the body to bind the soul to.
Though there are persistent rumors about "cyber zombies"... Well, from a meta-gaming perspective you CAN survive with a sub-zero essence. Sort of. But that requires cybermancy - magically binding the soul to what remains of your meat body. And it requires constant reinforcements of the spells, since your soul will do its best to escape. This is almost exclusively done with corporate backing -- it's too expensive for anyone else.
IMC, the lower your essence is, the more "cold" and machinelike you become. I had an NPC in a campaign that had 0.10 Essence. He basically spent his days off sitting at home staring at a wall. And when the pizza guy knocks on the door he has a gun drawn and pointed at the door in about 0,042 seconds.

What I really love with SR is all the secrets and metaplots. Who killed Dunkelzahn? (Oh, that one I know.) What's the meaning of Dunkelzahn's will? Who is The Laughing Man? What are the shedim? Who created the virus that caused the Crash of '29?
Shadowrun is a massive world. I could keep a campaign going on for ever without touching all secrets and metaplots.