I think human right to privacy shouldn't be violated in anyway unless the human is involved in serious crimes or some suspicious activities. And even when ID becomes necessary, it should be handled with care to prevent it from going into the wrong hands.
Well it's somewhat strange I must say to present one's ID inorder to make purchases of something and if that should occur I think there have been a hack in the system that will necessarily need one to undergo such process inorder to buy anything online. And moreso like you said violation of rights to privacy can also warrant that necessity for requiring numbers and ID but we should be on the safer side.