$5.00 Is not a lot of money, but I would also want to know why I was charged without reason. The people who are attacking this guy seem to be the ones who try to prove that they are financially well off. I'm sure if you see an extra $5.00 added to a store purchase you would question it as well, or try to find out whats up.
I never had this happen to me, but it could possibly be that your account was not actively being used prior to the second activation charge.
