I was thinking about all of the disc-media systems that have been released and how their copy protection was handled. I am not compiling this list to figure out how to pirate anything, but I'm just curious to see how it has gone. Please correct any errors you see...

Sega CD - nothing, assumed no one could copy CDs.
Turbografx 16 - nothing, assumed no one could copy CDs.
3DO - nothing, assumed no one could copy CDs.
Jaguar CD - encryption code supposedly made by an employee making a noise into a microphone
Saturn - outer ring of data that was outside of the readable scope
PSX - Bad blocks (data unreadable by normal CD players at the time) and code used in a limited number of games to see if the system was modded.
Dreamcast - new disc format. Rendered useless after Sega was found out to have left a "back door" open to play burned software
PS2 - contains logical and physical changes that cannot be duplicated by the burner
GameCube - Different sort of media, current burners can't replicate
Xbox - contains logical and physical changes that cannot be duplicated by the burner

Is that it? I'm trying to figure out where we've been and where we're going with console copy protection. Please, feel free to correct me where I'm mistaken.

Of note: If you are a pirate, please don't post. I don't care about how the system is defeated, but just what the system is.