Internally routed brake and shift cables pass through the bottom bracket (from the down tube to a chainstay), where—if they're slack—they will rest against the frame and away from the spindle, but where—if they're taut—they risk touching the continuously turning spindle. Or vice-versa if the cables are above the spindle.
If they do touch the spindle, then sooner or later the housing will be worn off, with the potential for an unpleasant incident such as leakage of brake fluid inside the frame.
What methods are being used to stop internally routed cables from touching the turning spindle? Is it ever the case, for instance, that the spindle is itself in a housing that does not rotate?