Hopefully someone can allay my fears concerning a powered USB hub.

I recently connected a powered USB to one of the ports of my G5. Several devices were then connected to it. On the other side of the G5 is another USB port that has an iLok plugged into it, but it has nothing to do with the USB hub.

When I shut the computer down (not put to sleep) I notice that the devices plugged into the hub are still receiving power. OK, but the strange thing is that the iLok key that is on a different USB connector (on the other side of the computer) is also receiving power. So it seems that the powered hub is sending power back into the computer's bus system even when the computer is off.

Is this safe? If anyone has any insight it would be much appreciated.