As mentioned before I have put up a well earthed 9 metre high mast for long distance radio stuff. And I usually make sure to leave things disconnected especially if any storms are about.
Well, one problem with earthing it of course is that it provides a better path to ground than if just on the concrete. But that's by the by, if it does get hit then it will (hopefully) all go to ground and not cause any damage. But being the highest metal object nearby until we get to the school flagpole a couple of blocks away, it could be a target! Especially with a big earth stake and a connection to ground.
A couple of weeks ago a big storm was approaching so I had pulled the plug. A friend in North Ryde told me he was getting some unusual reception from New Caledonia on FM, so seeing as there were no close CGs decided to hook it up again briefly for a check. Just after I turned the radio on there was a big buzzing noise through the receiver followed almost immediately by a big intra cloud bolt up above. Now being FM that is normally fairly immune to lightning static unless really strong, and I the buzzing lasted a couple of seconds I suspect it could well have been caused by a leader coming up from the mast (that luckily didn't connect). No way of proving that's what it was, but it started before the bolt and finished as the flash up above happened.