Apple has implemented a slight, but significant change to the way it books Genius Bar appointments online. Now folks wishing to make such an appointment must have a working Apple ID and password. Previously, users could simply enter in basic identifiable information like their name and email address in order to set up an appointment.
TechCrunch adds some insight as to the reasoning behind the recent change:
An additional reason for this change, we understand, is to give the control of a Genius Bar appointment to a user directly, who must know their credentials and enter them before being able to confirm a payment. There is also the convenience of having a customer's data automatically filled out with a simple entry of the Apple ID. This could allow Geniuses to look [up] past purchases and communicate with the user much easier now as well.