How many times can airplanes crash, before we ban them as too risky? How many times can people have car accidents before we ban driving automobiles, because it could hurt other people?
They took the experiment to a professional explosives range. The people who run that had a choice to say no, if they thought there was a serious risk. How much more "restraint" do you want?
Ok, well then maybe an additional question is 'At what point are the ends (entertainment) not worth the risks?'
That supposes the only ends are entertainment. It also ignores the very real possibility that without a venue such as Mythbusters, there would be even more guys in back garages doing stunts like my ex did - a homemade fireworks show that started a small fire; nearly blowing out the wall with an 1/100th scale cannon, and others I probably don't know about.
At least with Mythbusters there's a venue to pose the question and some number of uninformed individuals aren't attempting these things with inadequate (or no) safety precautions.
The more important question is how many people *don't* do something because they saw it on Mythbusters, vs. the number who *do*, despite the "don't try this at home" warnings.
I watch it rarely enough that I can't tell you much that I've meaningfully learned, but I do know more about what safety mechanisms are integral on a hot water tank, and why they're there, and the worst case scenario if they were over-ridden or cascade failed.
Because I'm a science and history geek, it's cool to know to what extent paper armor was as effective as steel armor, and why it hit a fail point. (For those who didn't see the episode, paper armor was 60-80 percent as effective, and posed a considerably lesser cost on the wearer physically. To have that much more energy with that small a loss in protection might be an acceptable trade-off for quite a while.)
I'm a writer; I like to know what would *really* happen if.. and I like to see the special effects debunked. I grew up with Dukes of Hazzard and Knight Rider - it was cool to see what would *really* happen to those cars had those stunts been real.
Entertainment? Information/Education? Edutainment? Your mileage may vary.