Surely if the average person is told "There's an X chance you'll die. There's a Y chance you'll lose a leg. There's a Z chance you'll be blown up", they'll worry unduly no matter what X,Y,Z are.

I can see what you're saying, that if you're a qualified doctor, or have studied medicine for years, then 23andme could be useful, but for everyone else, I think it could be very dangerous.