It's rare, isn't it, for any
current to go back through the ground or a grounding rod?

I thought so until I did some research. There are several situations
where
there can be dangerous current in the ground wire at the ground rod.

Obviously, a fault in the neutral will cause current to use the ground
wire as a return path, but also if your neighbor has a fault in his
neutral his current could be returning to the transformer via your
ground
rod.

Moral: before disconnecting the ground wire to service the ground rod
always check for current. Even if the main is off.

Thanks for all the replies.