Unplugging charged cell phones saves energy

An interesting article from cnet.com illuminates an issue: Plugged in cell phones that are fully charged waste energy.

If 10 percent of the world's cell phone owners did this (unplug their cell phones) ... it would reduce energy consumption by an amount equivalent to that used by 60,000 European homes per year.

I suppose this goes for other devices that we plug into our electrical outlets? I wonder if this energy savings comes into play if the cell phone is off but plugged in?

Is it that the A/C is supplying the energy to keep the phone on? Many more questions come out of this, but perhaps it's a good idea just to charge your cell phone and then unplug it.