I used to work in customer services for a public company, as a result I got threatened in writing and over the phone. Not that often, as naturally I was better at the job than most of my colleagues . I shrugged a particularly abusive threat off with my normal laid back attitude, but as I have a reasonably rare second name a brick went through my parents window. I didn't live there, but the phone book showed that as the only second name listed in the town.
The police linked it to my job and he went to jail, he had a long list of similar "crimes against the establishment". So if I was a speedway rider and someone threatened me with a breezeblock I would indeed be concerned. There are some strange people out there.