To add to Jon's post, many (if not all) 220v power areas have one end of the secondary grounded, meaning the ground rod would be using the earth as a voltage-divider resistor.
If this is true, your resulting voltage could be anywhere between 220 and 0. If I am wrong, you'd be getting an unreliable voltage anyway, because earth resistance is not a constant.
In either case, the voltage applied to the load will vary with the current usage (or, more accurately, the load impedance as it attempts to vary the current). You can also create dangerous voltage gradients in the earth.
Bottom line: it's a bad, bad idea.
