I get folks from the POS companies (get your minds out of the gutter...it means "Point Of Sale" in this context) who tell me that their electronic cash register absolutely HAS to have an isolated ground because it's susceptible to electronic disturbances and electromagnetic fields.
The real kicker is that I know of one in downtown Chicago that is working fine on a regular 20A circuit...despite being direct above one of the double-ended 5kV 2500kVA basement substation transformers.
Susceptible my butt...they just have this silly notion that their dinky little PC has the same power needs as an old fashioned mainframe computer with an air conditioner room and a raised floor.
