Exactly. I'm a little appalled at the rampant speculation, the apologetics in Mythbuster's favor, and the blind raging and blaming against them. We need to know the actual facts of what went wrong before we can make any determination of:
a - who was at fault
b - what actions are reasonable to ensure this never happens again
c - what repercussions might be appropriate
For all any of you know, there was a bad mix of powder. Or a mislabeled measuring cup. Or a rusty screw that broke loose at the exact wrong moment and allowed an unexpected pivot in the cannon. Those are nonsense reasons of course - we simply don't know yet what actually went wrong at the firing range.
Re: the apologetics in Mythbuster's favor, keep in mind, these guys are pretty damned rigorous when it comes to safety. Fire and EMS on site, clearing their experiments with local authorities, etc. Having them take the piss with something of this magnitude seems highly unlikely.