Do you have to call them for replacement? How do you know if your's is bad
Look at your power adapter. If it has a green dot in the corner it is good. If not, you can take your power adapter to any apple store or file for an exchange at.
I don't think they really care, you'll just be one less person that can sue them (when you shock the crap out of yourself using the old one AFTER they sent you a new one).