There new air terminals available that have a "mushroom" type head to eliminate the impalement hazard. I didn't see them in the catalog that BJ linked to, but I know that that company has them because the first time I saw them was at their booth at a trade show. Don
At the job I am at now they put Rebar caps (orange plastic mushrooms) on the airterminals during the work day and remove them at night to protect the workers on the roof from the sharp points.
I was under the impression that a lightning rod has a very sharp point on it to help eliminate the splatter when the bolt hits it. I might be wrong though but that is what I was told.