on the other hand, burning man seems to select for people who want to win a darwin award, so i'm kind of surprised at the low death rate.
Can you back up your claims?
Have you actually been to Burning Man?
I'd also point out that saying 50% of attendees are X doesn't really mean much. Hypothetically, If 0.1% of normal society take absurdly stupid risks, and 0.3% of burning man people take absurdly stupid risks, that would still be selecting for people who take absurd stupid risks.