"There are some countries in world where major protein source is peanuts and they don't have allergy problems."
True. And conversely, the incidence of peanut allergy in the USA is alarmingly high - and peanut butter is practically kids' staple diet. It's all very wierd.
AFAIK no-one has got to the bottom of what is causing the increase in peanut/nut allergy. But there does appear to be some consensus that exposure to nut proteins in early childhood might be a factor. That being the case, I personally feel that avoiding it is a good idea, especially if you have allergic tendencies in the family. It's not as if many people need to eat peanut butter. And living with a nut allergy is, frankly, a PITA, which you want to avoid if you can!
Twinmummy - with a family history of hay fever and one of the children having a bee sting allergy, I would definitely avoid peanut butter for the time being. That's my personal opinion. I am not a medic. Just a mother with allergies to contend with, acting on such advice as I've been given.
DD1 also has a bee sting allergy. After she had that reaction (on her second birthday), we saw a Consultant, who in fact advised that we avoid exposing her to any nuts until she is at least five. After that, she will be referred for proper allergy testing. I'm not sure where we go from there.
That advice was in the context of DH also being nut allergic, but I had the impression the advice would have been the same, even without that history, because of her reaction to the bee sting.