Power down your computer. (assuming it was a desktop unit and that Sheryl's was too). Now, follow the LAN cord that goes from your internet box(your DSL modem/router) to the back of your computer. Notice the light on ? Notice also that if you power down your computer, your DSL box still shows (the ethernet light is on) that it is connected to a computer. Unplug the cable , the light goes out.
The government has other ways. They have been able to detect data on computers via the power cable as well. They said that it would require a modem for the computer to respond, but who really knows once they have figured out how to detect it what they could do.
You got that explanation right and most people have no clue the net card is powered when a computer is off. (or appears to be off)
It is a useful tool but lawyers, who infect government like cancer, are great at manipulating useful tools for no good.
PGP does work!