Apple must need to know who you are as soon as you log in for this to work. Presumably this only works if you have some kind of Apple account. Do Macs call home each time a user logs into a Mac? If so, are Mac users generally aware and OK with this?
Just like Microsoft and Google.
Edit: The Apple Push Notification Service documentation at https://developer.apple.com/library/ios/documentation/Networ... talks about the architecture and seems to match my recollection.