I have one pretty new ACER 5552G laptop that cam with with Delta Electronics ADP-90CD D8 power supply that has grounding practice different from other laptops I have seen (normally grounded or floating):
The power supply output (otherwise floating) – side seems to be connected to mains ground through 1 kohms resistance on the power supply. This keeps the laptop pretty near ground and avoids ground loop problems. This is kind of “ground lift” circuit built into power supply.
I measured 110 mV DC between laptop case and mains ground. When I measured the current that flows from laptop case ground to mains ground I got around 0.1 mA DC and 0.03mA AC. Very low currents that should not cause problems.