First post here, and I couldn't help but post after reading this!
A little off the topic, but I have seen and FELT a strong arc from a ground wire to building steel. I was but a wee apprentice at the time, and it was the EBJ for an MRI room, which is basically a steel and concrete vault supposedly isolated from all other steel for shielding outside frequency. We had to move a 150 amp 480V three phase feed for the equipment in the room, which the disconnecting means was actually in "normal" space outside of the MRI room. The plans called for something along the lines of a 2/0 ground from the RF filter panel (a stainless steel access panel to inside the room that all electrical RF filters connect to mechanically) to building steel. The ground from this panel had been disconnected for about an hour, and the journeyman working with me warned me to treat the ground wire like it was hot. I thought he was kidding, but sure enough once I was well grounded I grabbed the ground wire and got a pretty good static belt. Even after leaving it disconnected for only a few seconds, you could see a visible arc as it was connected to ground.
I know it was a little off topic, but I thought it was interesting.
Actually in the same building we got a call for computer systems frying up, come to find out the 120/208Y transformer that fed all 120V outlets was never bonded. We shut down, bonded the neutral, and the problem cleared itself. But before I could take a meter and read 124V between the neutral and ground anywhere in the building. Yikes!