I think it's probably like drunk driving -- most of the times it doesn't result in anything bad, but there's a non-negligible chance of outcomes so bad that the expected value still comes out negative.

Or like drunk driving on your own property, where there is no other traffic nor pedestrians, and you are alone in your car (well, ok, you are in the car with another person, but s/he is drunk as well, knows you are drunk, knows the risks of drunk driving and half of the time replaces you behind the wheel). Should it be illegal? (assuming there are no (health) insurance issues if you crash&injure yourself)