I believe it's not the peanuts themselves that are bad for the birds (unless they're salted) but the fungus (bacteria?? I forget what it is) that comes on them. Some people will not give any peanuts or even peanut butter to their birds. I've heard others say the chance of them getting sick is pretty slim. We let our birds have whatever peanuts come in their parrot mix and peanut butter. Otherwise, they don't get any peanuts.
... Here's the funny thing with peanuts ... it's not the peanuts, but it is a fungus that grows in the ground and can form on the inside of the shell and contaminate the nut. I don't feed peanuts as almonds, pecans and walnuts are great alternatives ... the other thing to keep in mind is that too many will make your fid fat very quickly. They should be limited to 1 to 2 nuts a day depending on activity level.
Some peanuts have Afflatoxins in them. It was an afflatoxin that took my nappy. It seems peanuts are the number one carrier and the fungus is totally invisible to the naked eye. I no longer feed any peanuts to my birds.