The humor that makes me laugh hardest is the material I know would offend or insult someone else. Apparently I am not alone in this view because my entire career is based on that universal law. The Dilbert comics that work best are the ones you can imagine your boss or coworker looking at and saying, "Uh-oh. I think that's me."
But offending isn't enough. The audience gets more out of humor if the messenger is putting himself in danger. When Dilbert first launched, I was still working my day job. Readers loved knowing that I was on the verge of getting fired every day. The order to fire me was actually given at one point, but in the end my employer decided to give me hopeless assignments and wait for me to quit. They figured it would look better.
Dilbert is still a dangerous job. This week I got a bunch of angry letters because of a comic where Alice says she realized her job was like a dung beetle trying to mate with an epileptic cow. I think I was added to a few extra death lists. If you laughed at that comic, it's probably at least partly because you knew I was taking a risk in creating it.
You also imagine that it must be awkward for me to publicly mock managers and executives and then bump into them socially, which happens daily. It probably would be awkward if I cared about that sort of thing. So while it isn't particularly scary for me, as a reader you can imagine what it might be like for you, and it probably translates as more dangerous that it is.
I think something similar is true with other performers. We enjoy jugglers more when they use chainsaws and torches. And no matter how much you hate it when a musician grabs his crotch while dancing, on some level it still works because you know other people hate it way more than you do, and you know the artist is getting complaints. He's paying a price for the crotch-grabbing, even if the rewards are greater.
Movie stars have inherently dangerous jobs, in terms of potential embarrassment for movie flops, or getting caught on film doing something odious. And even the most seasoned professionals get scared to death when performing live. Most people couldn't handle that sort of pressure and know it. I think it is partly the perceived danger that makes celebrities exciting to us.
If art doesn't seem dangerous for the artist, it probably isn't relevant.