But really it is the ground loop issue which is always there with each chassis grounded through the ac cord as well as through the interconnects to other chassis.It should be pointed out that this is potentially an issue just with equipment that is interfaced via single-ended (unbalanced rca) interconnects, because inter-chassis noise currents that may be present flow through the shield or other return conductor of single-ended interconnects in common with signal return currents. Balanced interfaces will normally be immune to that effect.
There is also, of course, a safety risk that arises from lifting grounds. If everything is in good condition the risk is extremely small, and I have the grounds lifted in my own system on all of the components other than the preamp, but it cannot be said that the risk is zero. There are several other threads in the recent past in which this has been debated.
Regards,
-- Al