AZ Jeff:
I'll defer to your expertise (I'm not prepared to say you're a government shill just
claiming to be a cellphone engineer
), but I did want to clarify something as far as "turn it off" for everybody.
"Turn it off" depends on the definition of "off." Nearly all consumer electronics are computer controlled, even to the degree of power control. As such, they're never completely off; rather, primary functions are disabled, but some logic (notably the power control logic) remains active. A real power switch--something that actually broke the circuit between the power source and the active components--would not allow the computer to keep running, so they're not used. Think about it this way: your TV remote turns the thing on and off. The remote is a wireless device, so the TV has to have some sort of receiver to get signals from the remote. If the remote turned the TV set completely off, how would the receiver process signals?
Answer: parts of the system stay on, and the power button is just a "soft" power button. Your computer does the same thing: if you press the power button, it doesn't interrupt power; it just sends a command to the system to say "hey, I'd like to power down now, if that's OK," and the system (usually) obliges. It doesn't go completely off, though; it keeps the power manamement system running (and that system includes the power button). If it were to power down completely, it wouldn't come on when you hit the power button, because there would be nothing to recognize "hey, he tried to turn me on! Maybe I should apply power to the rest of the machine."
Cell phones work the same way. They use a "soft" power-off to go to sleep, but the only way to shut off everything is to remove power; failing a real power switch (which none of them have), you have to remove the battery.
Again, I'd be inclined to take AZ Jeff's word for what is on which power bus, but as for the claim that you can't turn it
completely off without removing the battery, yeah, I'd agree with that.