Medic Alert tags are invaluable to emergency personnel. And that's all I have to say about that.

As for the psychological aspect (whether wearing one sets up a person to have an acute attack), I don't buy it. In fact, I think it could be the opposite. For example, my dad, who is epileptic and also very forgetful, does not wear one. I wish he would, b/c when he saw it he'd remember to take his medications, and then he wouldn't scare us all half to death by having seizures. I'm not sure how to put it any better than that.