Well, Guest 3:11pm what I've read has said that about 20% of children outgrow their nut allergies. I have also found where most nut allergies are developed as adults. Speaking as someone who has many allergies I would never expect others to ban something on my behalf...I simply removed myself from the situation. As for the airlines, I'm willing to take the chance that I will not be flying on the exact flight as one of the only 3 million Americans with a nut allergy.
As for choking, it's possible to choke on anything that is put in one's mouth so that's not a valid argument in my opinion.