> Separating out the clients from the servers meant the designers had to really think about the interface. It meant clients couldn't just scribble all over the frame buffer however they liked. And it meant the server could usually prevent disobedient or insane clients from taking the system down.
Uh... X does a *really bad* job of this, actually. There are some security extensions these days whose details I'm not familiar with, but at least in classic X, any application can do pretty much anything it wants to -- scribble all over the screen, snoop all input events, lock up the server, change the contents of other app's windows...