PID control of a mass-spring-damper (Kevin Lynch)

For more information, see nu32.org. This video is a supplement to the book "Embedded Computing and Mechatronics with the PIC32 Microcontroller," Lynch, Marchuk, and Elwin. It is part of Northwestern University's ME 333 Introduction to Mechatronics.
L-comp: The virtual damper provided by the derivative gain Kd has no impact on the steady-state position of the mass. (It just wants the mass to stop moving, it doesn't care where.) Explain why a PID controller with Ki = 0 can never achieve zero steady state error of the mass-spring-damper position.