Using linear encoders.

Can you use linear encoders in a servo system? This would be on a
Bridgeport type machine with ball screws. I can see where any backlash,
no mater how small, would result in a continual hunting for position.
However, I know that there is at least one commercial CNC conversion system
that uses the linear scales for feedback.

Is this a reasonable thing to do or should I go with the rotary encodes
mounted on the servo motors.

Thanks,
Pete.